Picture of Allergic Contact Dermatitis (Arm)
Allergic contact dermatitis (reaction to temporary tattoo). Contact allergy to temporary tattoos has become an increasingly common phenomenon. In most cases, the tattoo material does not contain pure henna, but is a mixture of brown henna with paraphenylenediamine (PPD) called black henna. The patient is allergic to PPD in the tatto. In fact, the concentration of PPD in black henna is higher than that seen in commercial hair dyes. After resolution of the eczematous skin eruption, postinflammatory hyperpigmentation may persist for a considerable period of time.
Text: WebMD Medical Reference