Prevalence of botanical extract allergy in patients with contact dermatitis

Background: Botanical extracts are used widely in over-the-counter products. They are primarily added for fragrance and their purported healing properties. Numerous case reports of allergic contact allergy to botanical extracts have been published; however, little is known regarding the prevalence of allergic reactions to botanical extracts. Objective: To determine the prevalence of allergic patch-test reactions to a collection of botanical extracts in patients referred for patch testing. Methods: A total of 140 patients were patch-tested to a study tray containing 47 botanical extracts. Patients were divided into two groups: (1) a high-risk group consisting of 21 patients with a clinical diagnosis of contact allergy who were using botanical products and whose contact dermatitis was not fully explained by testing to standard allergens and (2) a control group consisting of 119 patients with no history of botanical extract use and who were being evaluated in a contact dermatitis clinic. Results: Ten of 21 patients (47.6%) in the high-risk group had at least one relevant botanical extract positive reaction. Only 4 patients (3.4%) in the control group had a relevant positive reaction. Four patients in the high-risk group had more than one relevant botanical reaction. Tea tree oil caused the most common relevant positive reaction. Conclusions: Contact allergy to botanicals was common in this highly selected group of patients. Contact dermatitis patients who use botanical products and whose reactions are not fully explained by standard patch testing may benefit from more extensive patch testing to botanical extracts.