Henna stain allergy is a reaction to ingredients often used in temporary tattoos created through a process known as mehndi. Traditionally associated with rituals in Indian, North African, Mediterranean and Asian cultures, this form of body-painting has recently become trendy in Western countries.

Henna is a plant-based coloring that rarely causes allergic reactions. However, additives sometimes used to enhance henna coloring or speed up the tattooing process have caused intense bouts of contact dermatitis in some people. There have also been reports of patients who immediately react to the henna paste after it is applied, displaying symptoms such as swelling, sneezing and difficulty breathing. The U.S. Food and Drug Administration (FDA) has singled out the “coal tar” dye p-phenylenediamine, also known as PPD, as a source of many of the problems associated with henna stain allergy.

The FDA has not approved henna for use in direct skin applications. Those who become sensitized to henna, PPD or other ingredients will remain at risk of reacting to those substances for the rest of their lives. Therefore, it is crucial to be aware of exactly which ingredients are being used to create the henna paste used by a mehndi artist or henna tattoo practitioner.