Contact dermatitis after temporary henna tattoos--an increasing phenomenon.

Four patients developed contact dermatitis to black henna tattoos on holiday in the Middle East and Asia. Two to ten days after skin painting an itchy, reddish swelling developed at the site of the tattoo exactly following its sharply demarcated borders. Histological investigation of the lesions revealed spongiotic dermatitis with dense lymphohistiocytic infiltrates. Patch testing in all patients showed a strong reaction to p-phenylenediamine (PPD). The other tests, including standard series and henna powder, were all negative. Healing time after application of topical class III and IV steroids was prolonged. These reports show an impressive side effect of temporary tattoos with possible long-term damage. Rather than henna, the causative agent in the pastes used for temporary tattoos appears to be PPD, a widely used dye that is added to the pastes in high concentrations to produce a darker shade. The growing incidence of this complication requires close observation, while practitioners should be aware of this sensitisation and of possible subsequent allergic reactions, especially after hair colouring with dyes based on PPD.