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.
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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 Food and Drug Administration 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.
PPD can also cause a delayed allergic reaction colloquially referred to as a skin eruption. In 2007, Dr. Gregory Sonnen of Baylor University 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 10 days after the application of a black henna tattoo by a street vendor. The allergic reaction developed into a weeping lesion before the subject received treatment with a topical ointment.
Long-Term Side Effects
Hypersensitivity reactions can lead to long-term side effects. Some post-inflammatory scarring and pigment changes can occur in the region of the reaction. Keloid scars, or rubbery collagen scars, can also form. Early reactions to PPD in children can also cause a lifelong hypersensitivity to the ingredient in hair dyes and dyed clothing, as well as an sensitivity to other allergens.