Allergic Contact Dermatitis to Pure Henna: A Systematic Review.

Henna has traditionally been considered safe as a natural dye for hair, skin and nails. However, recent reports of dermatitis are increasing. While often linked to para-phenyldiamine (PPD) additives, allergic reactions to pure henna are also emerging. This review aims to provide a focused clinical overview of allergic contact dermatitis (ACD) caused specifically by pure henna. We performed a systematic review of studies reporting on cases of ACD to pure henna. We searched PubMed, SCOPUS and Web of Science without time or language limits. Eligible studies required patch test-confirmed ACD to pure henna, excluding black henna, additives and reviews. Two reviewers independently screened titles, abstracts and full texts. Data on study details, patient characteristics, clinical features, patch testing techniques and treatments were extracted. Of 731 records, 13 met inclusion criteria for ACD to pure henna. Most cases involved women, though children were also affected. Reactions ranged from localised dermatitis to immediate hypersensitivity. Delayed forms were most common, occasionally bullous or pigmented. Patch testing remains the gold standard for delayed reactions, while prick testing aids in immediate hypersensitivity. Management mainly relies on avoidance. Corticosteroids, antihistamines and antibiotics were used in severe cases. Clinicians should remain aware of this uncommon but possible allergy.