Aromatherapy Undiluted- Safety and Ethics

by Tony Burfield and Sylla Sheppard-Hanger (2005)

Modified from an article - A Brief Safety Guidance on Essential Oils for the IFA.

Please note that the first version was in a different software format.Some
remnants of that may remain, such as a . mark instead of an '

In the last 20 years aromatherapy has spread its influence to the household,
toiletries and personal care areas: consumer products claiming to relax or
invigorate our psyche's have invaded our bathrooms, kitchen and living room
areas. The numbers of therapists using essential oils in Europe and the USA
has grown from a handful in the early 1980's to thousands now worldwide. We
have had time to add to our bank of knowledge on essential oils from reflecting
on many decades of aromatherapeutic development and history, the collection
of anecdotal information from practicing therapists, as well as from clinical &
scientific investigations. We have also had enough time to consider the risks in
employing essential oils in therapy. In the last twenty years, many more
people have had accidents, been 'burnt', developed rashes, become allergic,
and become sensitized to our beloved tools. Why is this?

In this paper, we hope to shed light on this issue, clarify current safety
findings, and discuss how Aromatherapists and those in the aromatherapy
trade (suppliers, spas, etc.) can interpret this data for continued safe practice.
After a refresher on current safety issues including carcinogenic and toxic oils,
irritant and photo-toxic oils, we will look at allergens, oils without formal
testing, pregnancy issues and medication interactions. We will address the
increasing numbers of cases of sensitization and the effect of diluting essential
oils. Last we will discuss the use of neat oils, including legal and ethical issues
and offer suggestions for safe practice for therapists as well as commercial
businesses (suppliers, spas).

In the last 5 years, some issues (such as anethole toxicity) have become of
slightly less concern, others (such as skin sensitization and methyl eugenol
carcinogenicity) have become more centre-stage, and many issues more
remain unresolved. Toxicological investigation of essential oils is a costly
business and there still remain huge gaps in our knowledge. For example, we
know little about inhalation toxicity, systemic toxicity, genetic effects, toxico-
kinetics, sub-chronic effects etc. of many of the commonly used essential oils,
and regulatory authorities in many countries are starting to demand this
information, under the threat that essential oils may be restricted or withdrawn
from sale to the general public if it is not provided. Whilst the aromatherapy
profession may be able to negotiate special status under the laws of many
countries to continue using these materials, we should, as a profession, at
least be aware of current safety issues affecting essential oils; historically,
most of this information has been generated from sister essential oil-using
industries, such as perfumery.

Safety has been defined before as freedom from danger, injury or damage (1).
Although many essential oils are potentially hazardous materials, if handled in
the appropriate manner, the risks involved in their use can be very small. So
therefore, most commercially offered essential oils are safe to use for the
purpose intended in a domestic/professional/clinical environment, if correctly
handled according to the producer's specific directions or the recommendations
of appropriate professional bodies. Detailed information on hazards, risks,
emergency and first aid measures and detailed toxicological data can be
located on the oil suppliers· MSDS's, which you, as an oil customer, have an
absolute legal right in law to receive, with the appropriate detail entered into
each of the 16 internationally established categories (don't be denied on this!).
Brief toxicological information on many individual essential oils in the related
field of perfumery can be found on the IFRA website Tisserand
and Balacs (2000) have written a useful book on The Safety of Essential Oils.
Martin Watt produced a Safety Data Manual called Plant Aromatics - Now out
of print.

Review of safety: Use the appropriate personal protection for the situation in
which you are working e.g. protective coat, goggles, safety gloves etc. if you
are decanting larger volumes of oil. All premises handling essential oils must
have an Eye-Wash Station.

Determine what is appropriate for your situation via a Safety Audit for your
working environment (if in doubt over how to do this consult your local Health
and Safety Department). Remember that in any situation, you are your own
Safety Officer! You have a duty of care for safety matters both to yourself and
to others around you!

N.B. It is not generally appreciated that spilled essential oils wiped up with
tissue/rags can autoxidise rapidly, especially in sunlight, posing a distinct
combustion hazard. This has lead to a number of serious fires within the
essential oil trade in recent years. Those oils containing citral are especially
predisposed towards this lemongrass (Cymbopogon flexuosus) and Litsea
cubeba oils on rag or tissue waste are notorious as fire-starters. All oil-
containing waste should be placed in a purpose-bought metal bin with an air-
tight fitting lid, and the bin contents safely disposed of outside the building, on
a nightly basis.

Methods of administration
Essential oils can be administered orally, topically, vaginally, rectally or by
inhalation, and different doses, degrees of absorption, metabolic processes and
biodegrative outcomes between oil constituents occur between these methods.
English/US aromatherapy practice has - up to now - been principally connected
to massage (and therefore to topical administration of essential oils), and in
many countries the National laws may not legally permit oral (or yet vaginal or
rectal) administration except by a medically qualified person. Nevertheless any
professional aromatherapy organisation with an international membership
should have a working knowledge base for all these applications. Dose:
aromatherapy massage typically uses essential oil concentrations from 1-2.5%
v/v in fixed vegetable massage oils in practice, with lower concentrations for
children and elderly people. Repeated client treatments with the same
essential oil are only recommended for the short to mid-term term period until
we know more about sub-chronic toxicity effects etc. of these materials and it
is worth remembering that a hard-working therapist or handler (supplier,
bottler) may be more exposed to the effects of essential oils than individual
clients! The use of neat essential oils in aromatherapy cannot be
because of the danger of irritation or sensitization reactions and
injuries caused to clients as result of this practice may not be covered by the
therapist's insurance.

Oils that are suspected carcinogens
A carcinogen is a chemical which may give rise to tumor production, which is
an unrestrained malignant proliferation of a somatic cell, resulting in a
progressively growing mass of abnormal tissue. Do not confuse with mutagens
which are substances which may cause heritable defects arising from their
action on mammalian germ cells: here tumor formation may result from their
action on somatic cells via cellular disruption. Whereas many mutagens are
carcinogens, not all carcinogens are mutagens. Teratogens are different again,
being substances that interfere with the normal development of either the
embryo or foetus in utero, giving rise to abnormalities in the neonate.

The following carcinogenic essential oils should not be used in
aromatherapy; the names in brackets refer to the carcinogenic items:

Birch tar oil crude (polynuclear hydrocarbons) Betula penda CAS No:8001-88-5
Cade oil crude (polynuclear hydrocarbons) Juniperus oxycedrus CAS No: 8013-

Some Croton oils such as C. tiglium & C. oblongifolius
Calamus oil (b- asarone type) Acorus calamus CAS No: 8015-79-0
Sassafras oils (safrole): Sassafras albidum CAS No: 8006-80-2
Ocotea cymbarum Brazil CAS No: 68917-09-9
Cinnamomum porrectum China

Oils that are Toxic
Acute oral (single dose) & dermal limit tests conducted by RIFM constitute
much of our knowledge of essential oil toxicity; there is only a much smaller
body of information on chronic- (6-30 month duration), sub-chronic- (up to 90
days), inhalatory- and immuno- toxicity. Some oils with LD50 values of less
than 1g/Kg are recommended by IFRA not to be used in perfumery (Boldo,
Mustard, Calamus, Chenopodium oils etc).

We are in a Catch-22 position with regard to the animal testing of essential
oils. For registration purposes under the exiting laws of many countries,
toxicological data (including oral LD50 tests) need to submitted and assessed
for new substances in order for the safety data information profiles to be
deemed satisfactory. But many oil-buying customers who are morally opposed
to animal testing, will not buy essential oils from companies who have assisted
or conducted recent animal testing on these items - this includes many or most
of the large International fragrance & flavour houses and many individual
aromatherapists. Cropwatch ( is campaigning for the
law to be changed in this area so that both oil-sellers and their customers are
not placed in this dilemma.

The substances in brackets represent particular items of toxicological

Almond oil bitter * (hydrocyanic acid) Prunus amygdalus CAS No: 8013-76-1
Armoise oil (thujones) Artemisia herba-alba CAS No: 8008-93-3
Boldo leaf oil (ascaridole) Peumus boldus CAS No: 8022-81-9
Calamus oil (b-asarone type) Acorus calamus CAS No: 8015-79-0
Chenopodium oil aka Wormseed (ascaridole) Chenopodium ambrosioides CAS
No: 8008-93-3
Croton oils with known toxicological properties, such as C. tiglium & C.
Horseradish oil (allyl & phenylethyl isocyanates) Amoracia rusticana CAS No.
Lanyana oil (thujones) Artemisia afra
Mustard oil (allyl isocyanate) Brassica spp. esp. B. nigra & B. juncea CAS No:
Parsley herb oil (dill apiole) Petroselenium crispum CAS No: 8000-68-8
Pennyroyal oil (pulegone) Mentha pulegium CAS No: 8007-44-1
Perilla oil (perilla ketone lung toxin) Perilla frutescens CAS No: 68132-21-8
Savin oil * (sabinyl acetate) Juniperus sabina CAS No: 68916-94-9
Sassafras oil * (safrole) Sassafras albidum CAS No: 8006-80-2
[Savoury oil, summer Satureja hortensis is classified T- toxic in many
Tansy oil (thujones) Tanacetum vulgare CAS No: 8016-87-3
Wintergreen oil (methyl salicylate) Gaultheria procumbens CAS No:68917-75-9
Wormwood oil (thujones) Artemisia absinthium CAS No: 8008-93-3

* Almond oil FFPA is normally traded in aromatherapy = almond oil bitter Free
From Prussic Acid (hydrocyanic acid).

* Sassafras oils (as safrole) are controlled under the Controlled Drugs
(Scheduled Substances used in Manufacture) (Intra-Community Trade)
Regulations 1993 and subsequent EU Directive 3677/90 as amended by
Council Regulation 900/92 as a Category 1 substance. In other words,
Sassafras oil cannot be bought or traded without registering with the Home
Office (UK).

Oils that are Photo-toxic
Photo-toxicity is light-related irritation, and involves precutaneous penetration
& bio-distribution of a light-activated substance in the dermis, followed by skin
exposure to light of the right wavelength and intensity. Therefore if photo-toxic
oils are applied to the skin, and exposure to bright light/UV lamps/sunshine
(especially at 312 to 320 nm wavelength) occurs over the next 12- 24 hours,
photo-toxic contact dermatitis effects may subsequently occur, due to re-
radiation of energy from the inherent furanocoumarin content or other
constituents of the oils:

Ford (1991) lists these materials which cause photo-toxic contact

Angelica root oil Angelica archangelica CAS No: 8015-64-3
Bergamot oil expressed Citrus aurantium ssp. bergamia CAS No: 8007-75-8
Cumin oil Cuminum cyminum CAS No: 8014-13-9
Fig leaf absolute Ficus carica CAS No: 68916-52-9
Lemon oil cold pressed Citrus limon CAS No: 8008-56-8
Lime oil expressed Citrus aurantifolia CAS No: 8008-26-2
Orange oil bitter Citrus aurantium CAS No: 68916-04-1
Rue oil Ruta graveolens CAS No: 8014-29-7
Tagete (oil & absolute) Tagete spp. CAS No: 8016-84-0
Verbena oil Lippia citriodora CAS No: 8024-12-2

Other oils may also be problematic as they also contain bergaptenes:
Amni visnaga oil Amni visnaga
Grapefruit oil expressed Citrus paradisi CAS No: 8016-20-4
Mandarin oil cold-pressed Citrus reticulata CAS No: 8008-31-9
Opoponax qualities Commiphora erythrea oil, absolute, resinoid: CAS No:
Parsley leaf oil Petroselinum crispum CAS No: 8000-68-8
Tangerine oil cold-pressed Citrus reticulata CAS No: 8008-31-9 or because they
contain the photo-toxic compound methyl N-methyl anthranilate

Petitgrain Mandarin oil Citrus reticulata var. mandarin CAS No: 8014-17-3
or from the thiophene content (tagete oil - also see addenda).

The IFRA Standard recommends that for fragrances not washed off the skin
and subsequently to be exposed to bright light, the total level of bergapten (5-
methoxypsarolen) should not exceed 15 ppm. Typical bergapten contents for a
number of the above photo-toxic oils are set out on the IFRA website

Citrus oils FCF (FuranoCoumarin Free) are sometimes recommended for
aromatherapy, but these oils (usually distilled from the expressed oils or whole
fruit slurries) are organoleptically merely pale shadows of the original
materials, and have poor keeping qualities.

Methyl eugenol has been identified as a potent rodent carcinogen, and occurs
in several essential oils, a few being:
Bay oil West Indian (Pimenta racemosa) CAS No: 8006-78-8..···. to 12.6%
Basil oils (Ocimum spp.) CAS No: 8015-73-4··. some chemotypes to 65%
Melaleuca oils-some (e.g. Melaleuca bracteata) ··········· to 50%
Nutmeg oil (Myristica fragrans) CAS No: 8008-45-58 ·······.. to 1.2%
Pimento oils (Pimenta officinalis) CAS No: 8006-77-7.. ······· to 15%
Rose oils (Rosa spp.) CAS No: 8007-01-0·.·············. to 3.0%

Oils that cause Irritation
An irritant is an agent which can cause cell damage if applied in sufficient
concentration and for a long enough period. Immunological processes are not
involved, and the chemical insult releases a potent vasodilator called histamine
from mast cells producing erythma and increased vascular permeability,
accompanied by eventual migration of polymorphonuclear leucocytes to the
area. Dermatitis can follow without prior sensitization. Those with fair skin are
more easily irritated, but the irritant reaction can also be shown to decline with
increasing age, and to increase with increasing temperature, such that irritant
dermatitis may only occur in some individuals in summer. The irritant must
exceed a certain threshold to produce a reaction, but the dose response curve
is less acute for allergens (Burfield 1999). Unlike sensitization, irritation
reactions fade when the insult is removed.

The following oils listed below can cause irritation effects. It will be noted
that a number of phenolic oils are contained in the list. Oils such as clove and
may chang are classified as R38: irritating to the skin.
Bay oil West Indian (Pimenta racemosa) CAS No: 8006-78-8
Clove oils (stem, leaf, bud) Syzygium aromaticum CAS No: 8000-34-8
May Chang oil aka Litsea cubeba CAS No: 68855-99-2
Melissa oil Melissa officinalis CAS No: 8014-71-9
Origanum oil Origanum vulgare & other spp. CAS No: 8007-11-2
Pimento berry & leaf oils Pimenta officinalis CAS No (berry): 8006-77-7. CAS.
(leaf): 8016-45-3
Summer Savoury oil Satureja hortensis CAS No: 8016-68-0
Winter Savoury oil Satureja montana CAS No: 8016-68-0
Tagetes oil Tagete spp. CAS No: 8016-84-0
Tea tree oil Melaleuca alternifolia CAS No: 68647-73-4
Thyme oil Thymus spp. CAS No: 8007-46-3
Turpentine oil Pinus spp. CAS No: 9000-64-0
The inclusion of Melissa oil in this list usually raises a few eyebrows; IFRA do
not recommend this oil for perfumery use.

Aspiration Hazards
Materials which can cause lung damage on ingestion are labeled Xn, R65, S62.
This applies to essential oils and oil blends containing over 10% hydrocarbons
(based on supplier information/analysis) and with a kinematic viscosity of less
than 7 x 10-6 m2/sec and with a surface tension of 33mN/m @25°C
(effectively most essential oils with hydrocarbon contents between 10% and
90% unless quite viscous, like vetiver oil from Vetiveria zizanoides). Examples
of oils labeled R65 are:
Bergamot oil Citrus aurantium ssp. bergamia 55% total hydrocarbons
Cedarwood oils (Cedrus spp.) ········.60% total hydrocarbons
Copaiba oil (Copaifera spp.)·········..80% total hydrocarbons
Ginger oil (Zingiber officinalis)········.90% total hydrocarbons
Manuka oil (Leptospermum scoparium)···..70% total hydrocarbons.

Allergens according to the EU 7th Amendment to the Cosmetic Act
An allergen is any substance that can trigger an inappropriate immune
response, or allergy, in susceptible people. Common allergens include animal
fur, dust, pollen and certain foods or medications. Fragrance allergy is believed
to occur in the general population at a level of around 1-2% (Nielsen & Menné
1993), but it may be much higher - for example in dermatology patients,
where some researchers are indicating an occurrence of 7-8%. There are often
problems in attributing reactions to a causative agent.

There is a requirement within the EU to label retailed cosmetic products
(including fragrances) that contain fragrances which show concentrations of 26
identified allergens above a certain (very low) limit, according to product. This
was derived largely from an SCCNFP Opinion on fragrance allergy in cosmetics
and non-food products intended for consumers in 1999, which originally listed
these 26 allergens (16 of which are natural and are found in essential oils).
These materials are alleged to cause skin sensitivity, or to be harmful in other
ways, and many essential oils may be involved by this legislation · in fact many
of the essential oils commonly used by aromatherapists to massage into the
skins of their subjects will contain levels of several of the 16 allergens
identified in SCCNFP opinion. These allergens will be applied to the skin in
normal aromatherapy practice at concentrations which are considerably more
(often by a factor of over 10 times) than the 0.01% limit identified for labeling
under the 7th Amendment to the EU Cosmetics Act. A list of these natural
allergens is set out below, with corresponding levels found in some essential
oils (according to the author) given in brackets.

SCCNFP OPINION & EU 7th Amendment to the Cosmetics Act.
(Tony B. additions in parenthesis)

para-Anisyl alcohol (found in Vanilla tahitensis beans)
Benzyl alcohol (to 4.5% in peru oil; also in ylang oils to 0.5%)
Benzyl benzoate (to 78% in peru oil; in tolu resinoid, ylang & cinnamon leaf
Benzyl cinnamate (to 0.8% benzoin resinoid)
Benzyl salicylate (to 5% in ylang ylang oil III)
Cinnamic aldehyde (to 88% in cassia oil; also in cinnamon bark oil)
Cinnamyl alcohol (54% in styrax oil)
Citral (to 75% in lemongrass oils; also Litsea cubeba, Melissa, Backhousia
citriodora etc)
Citronellol (to 43% in geranium oil Chinese)
Coumarin (to 65% in tonka bean absolute; in deertongue resinoid & to 0.1% in
Eugenol (> 90% in clove & pimento oils)
Farnesol (to 4.5% in neroli oil, 1% in rose oil)
Geraniol (90% + in palmarosa oil; in geranium oils)
Isoeugenol (<0.5% in ylang ylang oil extra)
Limonene (to 96% in sweet orange oil; in citrus, pine & mint oils & many other
Linalol (98% + in rectified ho oil; in rosewood oil, coriander & linaloe oils;

Comment: This brings us into an interesting area. Palmarosa oil (Cymbopogon
martinii) for example has a geraniol content of 80% - 90%, listed as a
sensitizer above, but was previously found to be non-sensitizing by RIFM. It is
postulated by Leopoittevin & Mutterer (1998) that geraniol acts as a pro-
hapten (see Sensitization) and is oxidized to the hapten geranial, which may
be responsible for sensitizing/allergenic effects. However there is an on-going
discussion as to whether there were impurities or oxidation products in the
synthetic items used for toxicological testing in the case of benzyl salicylate,
coumarin and linalol at least, since 100% pure items do not give these
reactions. Further, a number of allergens identified by the SCCNFP may be
weak, and/or rarely cause sensitization (see below).

We thus may have a situation where erroneous (extrapolated) conclusions
have been made by the dermatologists conducting the tests. This situation
leads to doubts about the true allergenicity of essential oils containing these
substances. But for now, aromatherapists should be aware of the issue of
allerginicity and review their treatment protocols in the light of this

Hand dermatitis in Massage Therapists
Crawford et al. (2004) investigated the self-reported and symptom based
prevalence of hand dermatitis in aromatherapy massage therapists in a 12-
month study finding it to occur at 15% and 23% respectively (compared to
reported rates of 2-12% in the general population). The study found significant
associations between the reporting of dermatitis and use of aromatherapy
products in massage oils and having a history of atopic dermatitis. Dorsal hand
dermatitis (49%) as opposed to palmer dermatitis was most prevalent, the
latter being typically associated with allergic contact dermatitis Interestingly
the therapists themselves cited frequent hand-washing as the most significant

Oils that have not undergone formal safety testing
Many essential oils used in aromatherapy in a more pan-global context have
not undergone formal safety testing, or if they have, the information is not in
the public domain which raises questions about ethical use in a professional
setting. Examples include those oils from Amni visnaga or from Catnip (Nepeta
spp.), and even more universally from familiar oils such as Niaouli (Melaleuca
quinquenervia) or Ravensara (Ravensara aromatica). Further, many oil
chemotypes used in aromatherapy such as Rosemary oil verbenone type
(Rosmarinus officinalis ct. verbenone) or Helichrysum italicum ssp. serotinum
also remain untested for safety or toxicity.

Pregnancy & Effects on the Reproductive System
Many essential oils are currently under examination for genotoxic effects. We
already know that sabinyl acetate is embryotoxic, fetotoxic, teratogenic and
abortifacient and is found in the following oils, which should not be used in
Plectranthus fruticosa oil
Spanish sage oil Salvia lavandulaefolia CAS No. 8016-65-7
Savin oil Juniperus sabina CAS No. 8024-00-8
Parsley herb and leaf oils and some chemotypes of the seed oil Petroselinum
crispum contain dill apiole to 20% which is severely hepatoxic and high dose
levels have (endangering the subject) been used to procure an abortion.
Vitex agnus-castus berry oil

Although some other essential oils may show a weakly estrogenic effect, Vitex
agnus-castus berry oil is sometimes used for ·hormonal balancing· by
aromatherapists: especially in post- and peri-menopausal women. There is
evidence that diterpenes in the oil cause circulating female hormone levels to
change, sometimes dramatically. The oil should therefore only be used under
medical monitoring and supervision (Lucks B. 2003-4; Sorenson J. 2003

Exposure to essential oils generally should be avoided/minimized during
pregnancy, especially during the first trimester. Many of the components of
essential oils, once they appear in the bloodstream, are probably capable of
crossing the placenta. Since we are largely unsure of de-toxicification routes in
foetal development, no 'expert' is capable of guaranteeing 100% safety
following short or long-term exposures to essential oils.

Vegetable Massage Oils
It is sometimes forgotten that skin sensitivity can be caused by vegetable
carrier oils, just as it can by essential oils. Further, the aromatherapist must
always be alert to possible client allergy to nut oils (almond, peanut,
macadamia, etc).

Interaction with medication
Certain essential oils can cause problems with subjects taking medication,
including those taking anti-coagulant and anti-depressive drugs. Problems with
grapefruit juice, and by inference, grapefruit oil, and Bitter Orange extracts
have been the subject of separate brief reviews by one of the authors (TB). In
general, if you are on medication, and until you have consulted your physician,
or have otherwise sought expert advice, avoid undue exposure to essential

Oils that cause Sensitization
Sensitizers can be dermal or respiratory. More usually in aromatherapy a
sensitizer is a substance that causes dermatitis only after alteration
(sensitization) of the skin by previous exposure to that substance (like a patch
test or in food as flavouring). It involves the immune system; the following
steps (permeation, metabolism, hapten production, antigen production) typify
the skin sensitization process *:

1. The chemical permeates the dermis, and undergoes bio-distribution.
Permeation is related to lipophilicity & molecular volume.

2. It is either metabolized by cutaneous enzymes or other processes to form a
reactive metabolite, or often may be chemically modified through the reaction
of UV light, or remains unchanged. The rate of conversion of pro-haptens to
haptens is important in sensitization. For example for the weak sensitizer
eugenol is oxidized to a highly reactive ortho-quinone hapten (in mouse
skin**) according to Lepoittevin & Mutterer (1998):

3. These so- produced reactive haptens bind to dermal proteins (haptens are
often electrophilic and can bind covalently with -NH2 groups and -SH groups
on proteins, modifying the protein, which when presented to the immune
system, will react with antigen-presenting cells in the dermis).

4. The Langerhans cells react with the allergen (the hapten-protein complex).
They then migrate to the thymus.

5. The Langerhans cells teach T-cells to recognize the allergen and when they
leave the thymus they are sensitized.

6. When they encounter the allergen they release lymphokines.

* After Lepoittevin & Mutterer (1998) & Burfield (1999).

** The author does not condone animal testing in any shape or form.

Under EC labeling laws, skin sensitizers are labeled Xi, R43.

According to the IFRA Hazards Working Group opinion (June 2004), ·quenching
phenomena· effects can still be taken into account (according to Section 3.3 of
the EU Dangerous Preparations Directive 88/379/EEC); however quenching
phenomena effects between eugenol and cinnamic aldehyde are now
unsupported according to the Notification No 4. of 38th Amendment to the
IFRA Standard (several authorities have questioned the whole concept of
quenching and declared the hypothesis as unsafe).

The following oils are responsible for severe sensitization effects and
should not be used in aromatherapy massage:

Cassia oil (cinnamic aldehyde, coumarin) Cinnamomum cassia CAS No: 8007-
Cinnamon bark oil (cinnamic aldehyde) Cinnamomum zeylanicum CAS No:
Costus oil, abs, concrete (sesquiterpene lactones) Saussurea lappa CAS No.
Elecampane oil (sesquiterpene lactones) Inula helenium CAS No: 1397-83-7
Fig leaf absolute Ficus carica CAS No: 68916-52-9
Massoia bark oil (massoia lactone) Cryptocarya massoia CAS No: 85085-26-3
Melissa oil (citral) Melissa officinalis CAS No: 8014-71-9
Oakmoss absolute etc. Evernia prunastri (non-IFRA compliant) CAS No: 9000-
Treemoss abs. Pseudoevernia furfuracea CAS No: 68648-41-9
Cedarmoss Evernia furfuracea qualities (resin acids)
Opoponax qualities Commiphora erythrea CAS No: 9000-78-6
Oxidized oils especially from Pinaceae (Pinus & Cypress spp.) and Citrus oils
(hydroperoxides) *
Peru balsam & oil Myroxylon pereirae CAS No: 8007-00-9
Styrax qualities Liquidamber spp. CAS No: 232-458-4. Resinoid: CAS No:
Oil: CAS No: 8024-01-9
Verbena absolute & oil Lippia citriodora CAS No: 8024-12-2
Tea absolute Camellia sinensis CAS No: 84650-73-4
Turpentine oil Pinus spp. CAS No: 8006-64-2

* IFRA recommends for example that oils from the Pinaceae e.g. Fir needle oil
Canada Abies balsamea should have a peroxide value of less than 10
millimoles of peroxide per litre.

Some fragrance houses internally restrict the use of bay laurel oil (Laurus
nobilis) in their fragrances because of customer sensitization issues.

Predictably also these essential oils marketed to aromatherapists are also

Backhousia citriodora oil (high citral/citronellal content)
Inula graveolens (sesquiterpene lactones)

N.B. Some aroma companies offer low sensitizer ranges of oils where
sensitizing constituents have been selectively removed by moved techniques
such as spinning cone distillation (also called centrifugal molecular distillation).
Of course, selectively removing components can affect their overall
physiological effects).

SENSITISERS & IRRITANTS: essential oil use in aromatherapy
In other professions, the use of essential oils may be restricted by legislation.
The infamous 7th Amendment to the EU Cosmetics Act requires a labeling
obligation (amongst other things) by March 2005 for a final cosmetic product
containing any of the 26 identified allergens present at 0.01% in products
rinsed off the skin, or 0.001% in leave-on products. Sixteen of these allergens
occur naturally in essential oils, and the SCCNFP in their 2002 Opinion made no
distinction between natural and synthetic allergens, a decision which IFRA and
the FMA are reportedly unhappy about (Rexpan 2004). In Europe this
legislation may therefore affect retailed aromatherapy massage oils and
essential oil blends, creams and lotions and bath products intended for a
cosmetic purpose, as well as natural and part-natural fragrances. Many
fragrance customers work to the principle that fragrance compounds (finished
fragrance concentrates prior to dilution in alcohol) should have limits of 1% of
R43 sensitizers and 20% of R38 irritants - but since the majority of essential
oils have some sort of risk coding under IFRA-IOFI the final risk coding may
mean employing sophisticated software to work out the appropriate labeling

The fall-out from the 7th Amendment doesn't apply to aromatherapists in their
practices (well not yet anyway) but the therapist practicing anywhere in the
world is required to disclose to the subject all possible adverse effects of the
proposed treatment and any associated risks under due diligence, and so this
area surely must therefore be discussed between therapist and subject in a
truly professional approach.

Professor Schnuck (Schnuck 2004) reported on work done by the IVDK, an
information network of dermatologists. He concluded that not all the 26
allergens identified by SCCNFP Opinion and enshrined in the 7th Amendment
to the Cosmetics Act bear the same risk, and criticized the EU Commission for
treating them all as equal. The report classified allergens accordingly (those 16
occurring in essential oils and naturally occurring aromatic materials.

1. Strong potent allergens: oak moss, tree moss, isoeugenol and cinnamic

2. Less potent allergens: cinnamic alcohol, hydroxycitronellal, HMPCC.

3. Rarely found as allergens: amyl cinnamic aldehyde, citral, eugenol, farnesol,
lilial, methyl heptine carbonate.

4. Risk of being an allergen too small to consider: amyl cinnamic alcohol,
benzyl alcohol, benzyl salicylate, geraniol, anisyl alcohol, benzyl benzoate,
benzyl cinnamate, citronellol, hexyl cinnamic aldehyde, d-limonene, linalool,
coumarin and alpha-ketone.

Comments on Schnuck's findings
Oils like cassia and cinnamon bark oil containing strong potent allergens such
as cinnamic aldehyde, and materials like and oakmoss & treemoss (category 1
above) are not (hopefully!) used in aromatherapy massage; few essential oils
contain the less potent allergen cinnamic alcohol (category 2 above). The use
of neat cinnamon bark oil on the skin would produce a moderate to severe
reaction in most people, which may become increasingly dramatic with
successive exposure events - as shown for example by a severe body rash on
the neck, face and arms, or via breathing difficulties, just from exposure to the

In Aromatherapy we might however use a number of oils from the 'rarely
found as allergens' category 3 above; for example citral-containing oils such as
lemongrass oil (to 90% citral) and Litsea cubeba (to 78% citral). Lalko & Api
(2004) quote figures on the potency of Litsea cubeba and lemongrass oil
(Cympopogon spp.) to promote skin sensitivity (at 8.4% and 6.5%
respectively) using the Local Lymph Node Assay Test, a result which is not far
removed from the figure for citral itself (6.3%). The authors also quote a NOEL
for citral of 0.5% for the induction of sensitization in humans. Since citral binds
to dermal proteins and stains the skin deep yellow for a number of days, we
probably aren't likely to use the undiluted over large exposed areas, especially
since citral is also an irritant as well as a sensitizer.

Eugenol also provides us with a particular problem - it is present in phenolic
oils such as clove leaf stem & bud oils (to 92% in leaf oil), pimento leaf (to
85%) and W.I. bay leaf oils (to 56%), and again is classified as both a
sensitizer, a moderate skin irritant and a severe mucous membrane irritant,
and Pederson et al. (2004) have already observed the augmentation of the
skins response to allergens in the presence of an irritant. The 38th Amendment
to the IFRA Standard (Nov 2003) states that the concentration limits for
eugenol in skin contact leave-on fragrance products is 0.5%, for rinse-off
products (including household cleaning products) is also 0.5% and for non skin
contact products 5%. When eugenol was tested recently at 5% on the skin of
human volunteers, the number of strong irritation skin reactions became so
excessive it was impossible to distinguish irritation from sensitization - twenty
six oils that contain eugenol are given in Annex 1 to the IFRA standard. The
use of clove oils at an absolute maximum of more than 0.6% concentration in
AT massage would therefore seem advisable - on this evidence the use of
higher concentrations would be foolhardy, if not downright dangerous.

Category 4 substances, which Schnuck considers the risk of being an allergen
too small to consider, gives us the most grief under EU legislation, since for
example limonene and linalol have a widespread, if not ubiquitous occurrence
in essential oils. But limonene is classified under UK CHIP regulations as an
irritant, sensitizer and as dangerous for the environment. Geraniol comprises
85% of palmarosa oil, and citronellol and geraniol make up a considerable
proportion of rose otto, which has been considered safe enough for
aromatherapeutic application for pregnant mums and babies up to now. It is
also apparent that in the case of coumarin being labeled an allergen, that the
science is incorrect and a manufacturer of pure coumarin has just recently sent
proof that it is not an allergen back to the SCCP (formerly the SCCNFP) for
reconsideration. This situation may apply to other alleged sensitizers. Use of d-
limonene and linalol containing essential oils have a reduced risk of adverse
skin if your supplier follows Good Manufacturing Procedures and adds an anti-
oxidant such as vitamin E to prevent the build up of sensitizing hydroperoxides
and their breakdown products.

Because of the rapid growth of aromatherapy practices since the internet has
arrived, the use of undiluted essentials oils has increased dramatically,
especially amongst holistic therapists and lay people who use oils without any
safety training. Uninformed people at trade shows, fairs, and hundreds of
entrepreneurial single trader businesses on the internet sell concoctions of
essential oils without a thought about any possible risks. Natural perfumers
(botanical formulators), untrained therapists, even consumers are using
undiluted oils on the skin without knowing they could be setting up setting up
the conditions for sensitization to occur. Sensitization is becoming the principle
problem of this profession, and the aromatherapy profession is largely in

One reason is that therapists were badly instructed by mentors or suppliers at
trade shows and conferences, or they may have read a popular high-street
book and decided that since oils are natural they will not be harmful. One
acupuncturist in her twenties that I (SSH) spoke to recently said that she
routinely puts several drops of some 2 or 3 neat essential oils directly onto her
hands and runs down the clients spine with this mixture first, before working
on the feet (still applying undiluted oils) - prior to commencing acupuncture
treatment. Since she learned the risks of this approach, she now dilutes her
oils, saving a lot of money, and achieving the same therapeutic effects (thus
far), keeping everyone safer and avoiding lawsuits.

Others are involved in the growing phenomenon called 'Raindrop Therapy',
which uses seven single neat oils (4-6 drops each: thyme, oregano, followed
by of cypress, birch, basil, and peppermint) neat, and 3 essential oil blends
(only 2 are diluted in almond oil). This concoction represents a huge dermal
insult from several milliliters of undiluted oils that are known-irritants being
dripped onto the spinal area of subjects backs. After working the oils in with
the fingertips along the spine, the area is covered with a warm towel “while
they rest” (Stewart, 2003). The diluent (V-6 mixing oil) was used only if the
“burn gets too bad”. This is followed by neat application again on the both legs
of 2-3 each drops of these 4 oils (in this order): cypress, birch, basil, and
peppermint ( These
treatments have become quite common in homes, spas, and treatment offices,
as they claim to cure everything from brain injury to scoliosis (which is “due to
a virus”). Testimonials abound for this miraculous cure, as they tend to do in
multilevel businesses, and the use of undiluted oils sells a lot of product up and
down line. Unfortunately horror stories also are emerging, as injured folks seek
relief and want to finally tell their story. Often the business owner trusts the
therapists and has no idea this is even being performed. Many injured parties
don't want to admit they got burnt (no pun intended), so few get reported to
the authorities, but it won't be long before someone gets sued over this. An
excellent overview is given in the White Paper mentioned above, which asserts
an opinion against the use of a technique using undiluted known-irritant oils
called "Raindrop Therapy", as it currently cannot be supported as a recognized
aromatherapy "best practice."

As an addenda, a manager of a high end resort/day spa and was horrified to
find out how their favorite (money-making) treatment could hurt someone,
saying “no one has ever complained” (SSH: private communication 2005). But
as we know, it is often difficult to establish legally the direct cause of
irritation/sensitization, and many are dissuaded from taking it further. A
positive development as a result of this episode is that the spa in question still
offers the same treatment but now dilutes the oils, reducing overheads, and
achieving the same results, so everyone rests easier at night. A simple and
safe solution.

Aromatherapists are reported as applying undiluted essential oils to the skin in
certain 'minor emergency' situations; tea tree oil for small skin traumas,
lavender oil for very minor burn areas, cajuput or niaouli oils for insect bites,
stings etc. etc. Some people think if we have a question as to use an oil or not,
to do a patch test (which few carry out), which now we know can actually set
up a sensitization reaction. Some think since they have never had a reaction,
it's not a problem, or with hundreds of clients we've not had any problems. Yet
how would they know? With many sensitization reactions it may be hard to
determine the exact origin of the problem.

Long ago many of us were poorly advised on how to use oils undiluted before
we knew better. Some of us saw Dr. Daniel Penoel apply oils neat to someone's
spine in a demo, even using a hair dryer to 'help absorption' with no warnings
about adverse reactions. Qualified medical practitioners may prescribe
essential oils for neat use or orally (in capsules) or larger than normal doses,
but legally they are qualified to practice medicine.

We hear charismatic speakers at conferences touting wondrous healings with
massive doses of irritant oils for clinical cases of severe infection or chronic
diseases. But for the majority of us using essential oils for health, very few are
appropriately qualified in appropriate disciplines, or even need to use essential
oils this way. And in light of the previous information available, in doing so is
endangering ourselves as therapists, endangering our clients and promoting
more reported skin problems from our oils in the world. At some point we have
to 'get real' and admit we have been mislead - the evidence from
dermatologists is already making us look unprofessional and I repeat, in

If you think about it, if relatively high amounts of essential oils are absorbed
and localized in the dermis as we claim, and can also enter the bloodstream via
inhalation, then the oils are physiologically active, and few us are qualified to
predict the consequences of this phenomena. In the case of birch, methyl
salicylate is quickly absorbed and large or repeated exposures may constitute a
toxic dose, especially to children. Do we know all medications our clients are
taking and the possible reactions? And do we really need to? Many ailments
only require a change of attitude, and just the exposure to low doses via the
sniffing of oils works well in that way!! Some with a more spiritually based
approach believe dropping the oils through the 'aura' affects the person, and it
may well do so, but if it's a frequency based phenomena at work, then the
diluted oils will theoretically work just as well as we see in homeopathy? (see
What the Bleep do we Know? )

Undiluted oils should not normally be used topically especially on sensitive
areas like the eyelids, on diseased skin, mucous membranes etc. due to the
risk of inflammation. It is conceded that many essential oils will contain
individual chemicals which have been separately shown to contain individual
irritants and sensitizer chemicals. Work is going on to establish when these
chemicals naturally occur in essential oils, they are equivalently adversely
active. It is fairly safely presumed in the meanwhile, that these substances
may only show their adverse effects if applied at a concentration above the
NOEL. So in other words, dilution is the safest method to proscribe.

In summary
Safety- armed with the forgoing information, we know that undiluted oils can
be inflammatory; and the use of undiluted essential oils is not safe. Not only
do they bring risks like burns and injury if undiluted, but also the risks of
sensitizing both your subject and yourself. Remember the healer's rule to first
“do no harm”. Why risk it?

Efficacy- is neat really better? We know that 'more is not always better', and
that diluted oils work just as well. It is also true that some essential oils show
one set of physiological properties at lower concentrations and another set of
effects at higher levels - for example 1,8-cineol-containing oils can show this
effect under certain conditions. It's also true that essential oils can produce
psycho-physiological effects at concentrations below odor threshold or odour
recognition levels.

Legal perspective - if we use oils undiluted, do they (as we say), 'penetrate the
skin' which could legally be considered administering a drug, and if so are we
practicing medicine without a license here? Not everyone agrees that diluted
oils necessarily penetrate faster or yet permeate the bloodstream. Some would
say they are held in the dermis as a 'reservoir' and may be acted on by P450
enzymes in the dermis, or meet other biological fates. We also don't know
much about toxio-kinetics - this being one of the areas that the SCCP have
criticized essential oil toxicology studies as being deficient in. So if we accept
we have progress to make in toxicological understanding, it makes sense to err
on the side of caution with sensible measures to protect ourselves, and to be

We do however know which oils should not be used on the skin, and how to
dilute them. If someone has a problem after a treatment you have given with
your product, and decides to sue you, do you have liability insurance? Is it up
to date? Do you really think you would stand a chance if you knowingly put a
well-known irritant/sensitizer on a client, who then develops a severe reaction
and decides to sue you? Would it be worse if you didn't dilute? Do you think it
matters to a judge if you have never seen or known of anyone who had a bad
reaction and therefore assumed it was safe? These are issues that should be
addressed if one chooses to use neat oils or an irritant/sensitizer.

Ethics- This topic is the crux of this entire paper and the take home message.
If the reader did not understand anything else, please understand this.
Ignorance is not an excuse and will not hold up in a court of law (at least in the
USA). When we use oils undiluted, or any of the toxic oils, or the known
irritant/sensitizers we break the first rule of healers: 'do no harm', because we
are a danger first to ourselves, secondly to our clients and third, our
profession. If you don't care about yourself, please care about your clients and
the entire aromatherapy profession, not to mention the health of the world.

As far as is known, this document has been assembled from current data
sources which are believed to be accurate and reliable, but the authors do not
claim that the information above is complete, and this data is supplied without
warranty, either expressed or implied, regarding its· correctness or accuracy. It
is the user's responsibility to determine safe conditions for the use of the
essential oils described above, and to assume liability for loss, injury, damage
or expense arising from improper use of these products.

Aka: also known as
CAS No: Chemical Abstracts Services number
CEFS: Committee of Flavour Experts
CHIP: Chemicals (Hazard Information and Packaging for Supply) Regulations
EU: European Union
FMA: Fragrance Manufacturers Association
IFRA: International Fragrance Research Association
FCT: Food & Cosmetics Toxicology
LD50: The dose (usually expressed in g/Kg) that kills 50% of a group of
matched animals (that were administered different doses).
MSDS: Material Safety Data Sheet
NOEL: no-observed-effect-level

Quenching: a phenomena whereby in predictive human skin sensitization
human testing, the expected sensitization effects of a fragrance allergen on
skin contact are reduced or nullified by the simultaneous presence of another

REXPAN: RIFM's expert panel
RIFM: Research Institute for Fragrance Materials
SCCNFP: Scientific Committee on Cosmetic and Non-Food Products
SCCP: Scientific Committee on Consumer Products
[Note: all CAS Nos. quoted above for essential oils are in the form of a US CAS

References-next page:
Bertrand F. et al. (1966) ·Skin sensitization to eugenol and iso-eugenol in mice:
possible metabolic pathways involving ortho-quinone and quinone methide
intermediates· Chem Res Toxicol 10, 335-343.

Burfield T. (1999) Safety Lecture to Aromatherapy Organisations Council. July 1999

Burfield T. (2004) Cropwatch 3 · see
Crawford G. et al. (2004) ·Use of Aromatherapy Products and Increased Risk of hand
Dermatitis in massage Therapists·. Arch Dermatol 140 (Aug 2004) 991-996.

Ehlers D. & Fister M. (1997) ·Compounds of Vanillons (Vanilla pompona Schniede)· J.
Essen Oil Res. 9, 427-431.

Ford R. (1991) The toxicology and safety of fragrances. In Muller PM, Lamparsky

D. (eds) Perfumes, Art, Science & Technology, pub. Elsevier New York pp441- 463.

Leopoittevin J.P. & Mutterer V. (1998) ·Molecular Aspects of Fragrance

Sensitization· in P.J. Frosch, J.D. Johansen, I.R. White (eds) Fragrances:

Beneficial & Adverse Effects pub Springer-Verlag 1998.
Lalko J. & Api A. 'Potency of Citral in the Local Lymph Node Assay' RIFM (Abstract No.
Lucks, Barbara (2003-4): aromatherapy newsgroup mails.

Nielsen N.H. & Menné T. (1992) 'Allergic contact sensitization in an unselected

Danish population'. The Glostrup Allergy Study, Denmark. Acta Dermatol Venereol
120, 33-36.

Pederson L.K., Johansen J.D., Held E. and Agner T. (2004) Augmentation of Skin

Response by Exposure to a combination of allergens and irritants - a review. Contact
Dermatitis 50(5), 265-273.

Rexpan (2004) RIFM Expert Panel Opinion on Essential Oils (internal document)
Rexpan Final Oct 4, 2004.

Schnuck (2004) Öko-Test No. 7/2004, 55.

Sorenson, Janina (2003): aromatherapy newsgroup mails.

Stewart, David, (2003), A Statistical Validation of Raindrop Techinque, Care
Publications, marble Hill, Missouri

Tisserand R. & Balacs T. (2000) Essential Oil Safety - a Guide for Health
Professionals. Churchill-Livingstone.


Copyright: Tony Burfield and Sylla Sheppard-Hanger © (2005)
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Advice on the safety issues of using essential oils