Henna is the powdered leaf of a certain plant. It is used to make medicine.
Don't confuse henna with henna root (Alkanna tinctoria), also referred to as alkanna root.
Henna is used for stomach ulcers, a type of inflammatory bowel disease (ulcerative colitis), bed sores, and other conditions, but there is no good scientific evidence to support these uses. There is also concern that using henna is unsafe when taken by mouth.
In manufacturing, henna is used in cosmetics, hair dyes, and hair care products. It is also used as a dye for nails, skin, and clothing.