Contact dermatitis following the application of temporary paint-on henna tattoos indicates a potentially serious problem of active sensitization. We describe 2 cases involving sisters who travelled to Bali together and acquired a temporary black henna tattoo to the lower back region. Both sisters subsequently developed a contact dermatitis at the tattoo site, the dermatitis disseminating in one sister. There was persistent hyperpigmentation at the tattoo site in both sisters several months after the application. Patch testing revealed a positive reaction to para-phenylenediamine (PPD) in both sisters. One sister also showed reactions to other hair dyes and to multiple organic dyes. Allergic contact dermatitis to PPD contained in temporary henna tattoos is an increasing problem worldwide, with cross-reaction to related compounds and permanent skin changes, a frequent consequence of sensitization to this significant allergen.