Honey flower dermatitis: Contact allergy to ellagic acid in Melianthus comosus

A case study is reported whereby a patient with no prior allergies developed a strong and spreading delayed-type hypersensitivity reaction to Melianthus plants, nectar and synthetic pigment derived from it after frequent handling of these substances. The lesions improved after treatment with topical steroids and allergen avoidance within 1–2 weeks. Subsequent patch testing with the plants, nectar and synthetic ingredients identified ellagic acid (EA) as the sensitizing agent. This is the first proven case of allergic contact dermatitis to EA, a phenolic substance present in numerous plants, fruits, and nuts regularly consumed by humans. Melianthus use is growing worldwide as an ornamental plant. Moreover, it is used in traditional South African medicine for its anti-inflammatory effects. In recent years, these extracts and EA have been added to natural, plant-based topical formulations for the treatment of inflammatory skin disorders. Our observation that the EA found in Melianthus can induce severe contact allergy should caution for the possible dangers of specific allergic sensitizations to these increasingly used additives in natural medicines.