Background: Recently, temporary paint-on tattoos have become increasingly popular as a safe alternative to permanent tattoos in Asia and other regions. The most common dye for such temporary tattoos is henna, a vegetable dye. Henna is considered to possess low allergenicity because the incidence of allergic contact dermatitis to henna has rarely been reported. However, recently, allergic reactions to henna used in temporary tattoos have been reported frequently.
Observations: Ten patients developed inflamed skin eruptions after receiving temporary paint-on tattoos in either Thailand or Indonesia. The 6 patients who were patch tested all exhibited moderate to strong positive reactions to p-phenylenediamine (1% in petrolatum). Four of the 6 patients were then tested with commercial black henna obtained from Thailand, and all 4 had strong positive reactions. A skin biopsy specimen showed lichenoid dermatitis. Mass spectrometry analysis of commercial black henna for molecular weight revealed a major peak at the mass-charge ratio of 108.1, which corresponds to the molecular weight of p-phenylenediamine.
Conclusions: The most likely causative agent for the lichenoid reaction associated with use of commercial black henna for temporary tattooing, currently popular in Southeast Asia, is p-phenylenediamine. With the increased popularity of temporary paint-on tattoos, clinicians should be aware of the possible associated complications.