What are essential oils?
Essential oils are volatile aromatic substances obtained from plant material through various methods including distillation and extraction. Essential oils have been widely used for centuries in aromatherapy, balneotherapy, and perfumery (see perfumes and fragrances). During aromatherapy, essential oils are often applied directly to the skin or delivered by inhalational methods. Essential oils are also increasingly being used in household products and in aerosol diffusers [1,2].
Commonly used essential oils include [1,3]:
- Tea tree oil (Melaleuca alternifolia oil)
- Ylang-ylang oil (I and II) (Cananga odorata oil)
- Lemongrass oil (Cymbopogon spp. oil)
- Sandalwood oil (Santalum album wood oil)
- Clove oil (Eugenia caryophyllus oil)
- Jasmine absolute oil (Jasminum officinale oil)
- Sweet bay (Laureal) oil (Laurel nobilis oil)
- Cedarwood oil (Juniperus virginiana wood oil)
- Patchouli oil (Pogostemon cablin oil)
- Neroli oil (Citrus aurantium flower oil)
- Peppermint oil (Mentha piperita oil)
- Narcissus absolute oil (Narcissus poeticus flower extract)
- Lemon oil (Citrus medica limonum oil)
- Eucalyptus oil (Eucalyptus globulus oil)
- Orange oil (Citrus aurantium dulcis oil)
What is allergic contact dermatitis to essential oils?
A number of essential oils are known to be allergenic. Essential oils that commonly cause allergic contact dermatitis include [1–3]:
- Tea tree oil
- Ylang-ylang oil (I and II)
- Lemongrass oil
- Sandalwood oil
- Clove oil
- Jasmine absolute oil
- Narcissus absolute oil.
Who gets allergic contact dermatitis to essential oils?
Allergic contact dermatitis to essential oils occurs more commonly in people with occupational exposure to essential oils [1,5,6]:
Other groups who risk allergic contact dermatitis to essential oils include [1,6]:
- People with atopic dermatitis
- Older patients
As a result of increasing use of essential oils in the home, there have been cases of airborne contact dermatitis caused by fragrance diffusers [7,8].
Essential oils are used in many countries such as Iran, India, China, and Thailand as a traditional topical therapy for stomach-ache and flatulence in infants. Localised eczematous reactions have been observed in the abdominal region of infants exposed to this therapy .
What causes allergic contact dermatitis to essential oils?
Allergic contact dermatitis is a delayed (type 4) hypersensitivity reaction that generally occurs 24–72 hours following exposure to an allergen. The mechanism involves recognition of the allergen by pre-sensitised T-lymphocytes, which release inflammatory cytokines that activate the skin immune system and cause dermatitis .
Each essential oil can have over 100 constituents . Often people with allergic contact dermatitis to essential oils react to many different oils, not just one, presumably because of shared constituents .
What are the clinical features of allergic contact dermatitis to essential oils?
The most common symptoms of allergic contact dermatitis are skin itching, redness, and scaling . These symptoms usually occur at the site of contact with the essential oil but can extend outside of this area.
In aromatherapists, the hands and forearms are most commonly affected with possible involvement of the face, neck, and legs [5,11,12]. Spread to other areas has also been reported . Symptoms usually improve with time spent away from work.
People who have been exposed to airborne essential oils can also have widespread involvement [7,8].
What are the complications of allergic contact dermatitis to essential oils?
People who work within the aromatherapy and massage industry can experience serious consequences of sensitisation to essential oils, which can result in them being unable to work . There can also be an impact on social activities and even permanent disability .
How is allergic contact dermatitis to essential oils diagnosed?
Clinical history and examination
A detailed history of exposure, together with the clinical features, morphology, and distribution of the lesions, are important in making the diagnosis of allergic contact dermatitis to essential oils.
In cases of occupational exposure to essential oils, symptoms often improve during holidays or weekends .
Patch testing is used to determine the cause of allergic contact dermatitis. Patches containing small amounts of potential allergens are applied to the back and then removed after 48 hours to observe for an allergic reaction, which manifests as localised eczema. The test site is observed again after an additional 48–96 hours .
Patients who are allergic to essential oils commonly have multiple sensitisations . Most patients with allergic contact dermatitis to essential oils also have positive reactions to fragrance mix I in the baseline series; however, extended patch testing is necessary, because not all affected patients are positive to fragrance mix I . Patch testing to the patient's own products is useful as the allergen may be an oxidised component .
Gas chromatography and mass spectrometry have been used experimentally to analyse essential oils in order to identify common allergens within them .
What is the differential diagnosis for allergic contact dermatitis to essential oils?
Conditions that may co-exist or be confused with allergic contact dermatitis to essential oils are:
Irritant contact dermatitis
Irritant contact dermatitis to essential oils in high concentrations can coexist with allergic contact dermatitis. Irritant contact dermatitis is confined to the area of contact with the offending substance, whereas allergic contact dermatitis can extend beyond the area of direct contact .
Contact urticaria presents as a weal-and-flare reaction within minutes of exposure to a substance and resolves within minutes to hours .
What is the treatment for allergic contact dermatitis to essential oils?
Prevention of allergic contact dermatitis to essential oils relies on allergen avoidance . In particular, people should be advised not to apply neat, undiluted oils directly to the skin, as this can lead to sensitisation .
- Gloves for hand protection should be considered; however, they might not be appropriate in some occupations, such as masseurs .
- Education is an essential part of prevention – counsel patients on allergen avoidance and barrier protection methods .
- Moisturisers and barrier creams may be used to soothe, protect, reduce dryness, and minimise the amount of topical steroid used.
- Systemic corticosteroids (eg, prednisone) and immune modulating agents may be used in widespread dermatitis or refractory cases.
- Oral antibiotics may be required for secondary bacterial infection.
- Oral antihistamines may be used for their sedative effect, but have no effect on the dermatitis .
What is the likely outcome for allergic contact dermatitis to essential oils?
Avoidance of the allergenic essential oils usually results in resolution of skin symptoms . In some cases, the symptoms persist and become chronic, especially if there is ongoing inadvertent low-dose exposure in daily life.