The FDA regularly issues warnings to consumers about avoiding any temporary tattoos labeled as black henna or pre-mixed henna as these may contain potentially harmful ingredients including silver nitrate, carmine, pyrogallol, disperse orange dye and chromium. Black henna gets its color from paraphenylenediamine (PPD), a textile dye approved by the FDA for human use only in hair coloring. In Canada, the use of PPD on the skin, including hair dye, is banned. Research has linked these and other ingredients to a range of health problems including allergic reactions, chronic inflammatory reactions, and late-onset allergic reactions to related clothing and hairdressing dyes. They can cause these reactions long after application. Neither black henna nor pre-mixed henna are approved for cosmetic use by the FDA.
Mainstream art galleries hold exhibitions of both conventional and custom tattoo designs, such as Beyond Skin, at the Museum of Croydon. Copyrighted tattoo designs that are mass-produced and sent to tattoo artists are known as "flash", a notable instance of industrial design. Flash sheets are prominently displayed in many tattoo parlors for the purpose of providing both inspiration and ready-made tattoo images to customers.