Can patients develop contact allergies to EOs?
The short answer is yes! Contact allergy to almost 80 EOs has been reported,15 including tea tree oil,16,17 ylang-ylang oil,17,18 lavender oil, peppermint oil,18 jasmine absolute,17 geranium oil, rose oil,18 turpentine oil,19,20 and sandalwood oil.18 The recent increased prevalence of allergic reactions to EOs likely is due to increased consumer use as well as increased detection from availability of commercial patch-test preparations.
Essential oils have many common ingredients. De Groot and Schmidt3 documented that 14 of 23 chemicals present in more than 80% of EOs have been reported to cause contact allergy. Interestingly, allergic patients often react to more than one EO, which may be explained by the many shared chemical components in EOs.
Essential oils are “natural” so they must be safe?
In general, most safety profiles are good, but rare toxic reactions from EOs have been observed.4 A recent Australian study reviewed EO exposure calls to the New South Wales Poisons Information Centre.21 The majority of EO poisonings were accidental or the result of therapeutic error such as mistaking EOs for liquid pharmaceuticals. Additionally, this study found that from July 2014 to June 2018, there was a 5% increase in the number of calls per year. More than half of EO poisoning calls involved children, with toddlers being the most frequent cases, suggesting the need for child-resistant top closures. The most frequently involved EOs in poisonings were eucalyptus (46.4% [n=2049]), tea tree (17% [n=749]), lavender (6.1% [n=271]), clove (4.1% [n=179]), and peppermint (3.5% [n=154]).21 Essential oils do not come without potential pitfalls.
What is the clinical presentation and workup?
The workup of EO allergic contact dermatitis begins with obtaining a history to evaluate for use of EO diffusers, perfumes, hygiene products, cosmetics, massage oils, toothpastes, and/or pharmaceutical products. Exploration of potential exposures through occupation, environment, and hobbies also is indicated. Clinical presentation is dependent on the mechanism of exposure. Contact allergy may result from direct application of an allergen to the skin or mucous membranes, contact with a contaminated environmental item (eg, lavender oil on a pillow), contact with EOs used by partners or coworkers (consort dermatitis), airborne exposure (EO diffusers), or systemic exposure (flavorings). Airborne dermatitis from EO diffusers may involve the exposed areas of the face, neck, forearms, arms, behind the earlobes, bilateral eyelids, nasolabial folds, and under the chin. History and clinical presentation can raise suspicion for allergic contact dermatitis, and patch testing is necessary to confirm the diagnosis.
How do we patch test for EO contact allergy?
There are many EOs commercially available for patch testing, and they typically are tested at 2% to 5% concentrations in petrolatum.15 A North American and European study of 62,354 patch-tested patients found that 7.4% of EO-positive individuals did not react to fragrance allergens in a standard screening series including fragrance mix I, fragrance mix II, and balsam of Peru, highlighting the importance of patch testing with specific EOs.22 Currently, only 3 EOs—tea tree oil, peppermint oil, and ylang-ylang oil—are included in the 2019-2020 North American Contact Dermatitis Group screening series, making supplemental testing for other EOs important if contact allergy is suspected; however, testing the patient’s own products is imperative, as there is strong variability in the composition of EOs. Additionally, aged oils may have been exposed to light, oxygen, or varying temperatures, which could result in the formation of additional allergenic chemicals not present in commercially available preparations.15 In addition to commercially available allergens, we test patient-provided EOs either as is in semi-open fashion (ie, EOs are applied to patient’s back with a cotton swab, allowed to dry, covered with adhesive tape, and read at the same interval as other patch tests23) or occasionally dilute them to 1% or 10% (in olive oil or mineral oil).
How should I manage a positive patch-test reaction to EOs?
Patients should avoid relevant EO allergens in their products and environment, which can be easily achieved with the use of the American Contact Dermatitis Society’s Contact Allergen Management Program or similar databases.
Final Interpretation
We are ubiquitously exposed to EOs every day—through the products we use at home, at work, and in our environment. Essential oils make their place in the world by providing sweet-smelling aromas in addition to their alleged therapeutic properties; however, beware, EOs may be the culprit of your next patient’s allergic contact dermatitis.