How should dermatologists manage contact allergies to botanicals?
Clinical Applications
Dr. Schwarzenberger is the former physician editor of DermWorld. She interviews the author of a recent study each month.
By Kathryn Schwarzenberger, MD, FAAD, June 1, 2024
In this month’s Clinical Applications column, DermWorld Physician Editor Kathryn Schwarzenberger, MD, FAAD, talks with Mark Denis P. Davis, MD, FAAD, and Anagha Bangalore Kumar, MBBS, from the Mayo Clinic, about their Dermatitis paper on ‘Results of Patch Testing to Botanicals: Review of the Mayo Clinic Experience Over 2 Decades.’
DermWorld: You and your colleagues recently looked at results of patch testing with botanicals at your institution over the past two decades. What constitutes a “botanical” and why should dermatologists be aware of this?
DermWorld: What does a contact allergy to botanicals typically look like? Are some areas of the body more likely to be affected?
Drs. Davis and Kumar: Contact allergies typically begin at the site of contact with the product. In the acute phase, it can present with itchy red patches or oozing and crusting. When severe, it can present at distant sites with smaller erythematous papules with “id phenomenon.” In the chronic phases, it can present with thickened dark patches or lichenification. Sites of involvement on the body correspond to the site of contact with the botanical product and can be localized or generalized. In our study including over 12,000 patients spanning two decades, the most common presentation was generalized dermatitis followed by dermatitis of the hands and dermatitis of the face.
DermWorld: It seems like botanicals are everywhere these days. Are we seeing rates of allergic reactions increasing over time?
Drs. Davis and Kumar: The global botanicals market was valued at $107.2 billion in 2022 and is estimated to have a 7% compound annual growth rate until 2030. The use of botanicals continues to increase in various industries especially those related to personal care, cosmetics, aromatherapy, and even the food and beverage industry. In our cohort over 20 years, we saw a statistically significant (p<0.001) upward trend in the number of patients that had a positive patch test to botanicals. The number of patients that had a positive test to at least one botanical agent was 7.8% between 1997-2003, 8.5% between 2004-2010, and rose to 17.1% between 2011-2017. These rates could have been from the increased use of botanicals in general as well as increased ability to test for larger number of botanical allergens.
DermWorld: Is there a “best test” if you suspect an allergic reaction to botanicals? Does the T.R.U.E. Test screen sufficiently for botanical allergy?
Drs. Davis and Kumar: The “best test” to determine a suspected allergic reaction would be patch testing with the patient’s product that was suspected to cause the reaction. This may often not be practical. In our institution, we offer patch testing with regular, extended, and botanicals and fragrances series in a patient suspected to have an allergic reaction to botanicals. History of exposure and the overall clinical picture are considered before offering patch testing. The commercially available T.R.U.E. screens for the 35 most common allergens including the most common botanicals, but is unfortunately not comprehensive.
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DermWorld: If a patient has a positive screen to one botanical, would you expect them to have cross-reactions to others? What about other fragrances? Should they avoid them entirely?
Drs. Davis and Kumar: About 20% of our patients tested positive to more than one botanical. In our study, the highest co-reactivity rates (5.4%) were observed between hydroperoxides of linalool 1.0% and Myroxylon pereirae resin 25%. However, it is hard to determine if this was clinically relevant. Co-reactivity occurs when different allergens have a positive patch test due to concomitant exposure. True cross reactivity occurs when someone allergic to a specific allergen has a positive reaction to another allergen due to structural similarity between the two allergens.
When a patient has a positive patch test, they are often given access to a database containing allergens they reacted to, their common co-reactors and cross reactors, and lists of products they could safely use or potentially avoid. When a patch test is considered clinically relevant, avoidance of exposure to the allergen is recommended.
DermWorld: Do you have any tips for dermatologists to help manage patients in whom they suspect have a contact allergy to botanicals? Have you had luck getting patients to stop using their essential oils?
Drs. Davis and Kumar: A thorough history for exposure, including occupational exposure, helps determine which patch test series could be used for testing. Management of allergic contact dermatitis focuses on avoiding the offending allergens. When patients have a positive reaction, they can be given access to databases like SkinSAFE (at Mayo Clinic) or Contact Allergen Management Program/CAMP (American Contact Dermatitis Society) which help patients develop a personalized list of products that are safe to use based on their sensitivities. It may not be practical to completely avoid the allergen at certain times. This may be due to the presence of the allergen in various products and in various concentrations. The composition of several fragrances is not revealed, and the chemical composition of several botanical products is still unknown. These factors make testing and avoidance of these allergens difficult.
Mark Denis P. Davis, MD, FAAD, is a dermatologist in the Department of Dermatology and a professor of dermatology at the Mayo Clinic in Rochester, Minnesota.
Anagha Bangalore Kumar, MBBS, is a dermatology resident at the Mayo Clinic. Their paper appeared in Dermatitis. The authors have no relevant financial or commercial conflicts of interest.
Disclaimer: The views and opinions expressed in this article do not necessarily reflect those of DermWorld.
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