Henna tattoos, or mehndi tattoos, play a traditional role in Mediterranean, Middle Eastern and Southeast Asian cultures. In India, for example, many people decorate themselves with henna tattoos during weddings and festivals such as Diwali. Though these tattoos are only temporary, they can have certain adverse side effects, particularly when additional ingredients are added to the pure henna powder to darken the paste. Check ingredient labels on henna paste, and do not purchase henna paste or get a henna tattoo if you cannot find a list of the ingredients.
Allergic Reactions
Some pre-mixed henna pastes have paraphenylenediamine, or PPD, added to them to darken the pigment. These henna pastes often go by the name "black henna." The United States Food and Drug Administration (FDA) approves PPD for use as a hair dye, but not for use on the skin. The inclusion of PPD in henna paste can cause allergic reactions on the skin.
Skin Eruption
PPD can also cause a delayed allergic reaction colloquially referred to as a skin eruption. In 2007, Dr. Gregory Sonnen of Baylor Univerity published a paper about one specific case of such a reaction, officially referred to as a "Type IV hypersensitivity reaction." The reaction did not occur until ten days after the application of a black henna tattoo by a street vendor. The allergic reaction developed into a erythematous papulovesicular weeping lesion, before the subject received treatment with a topical ointment.
Long-Term Side Effects
Hypersensitivity reactions such as the one described above can lead to several long-term side effects. Some post-inflammatory scarring can occur in the region of the reaction, as well as pigment changes. Keloid scars, or rubbery collagen scars, can also form. Early reactions to PPD in children can also cause a lifelong oversensitivity to the ingredient in hair dyes and dyed clothing, as well as an oversensitivity to other allergens.
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