Selenium sulfide

Selenium sulfide (also selenium sulphide; see spelling) is an antifungal agent often used in shampoos for the treatment of dandruff and seborrheic dermatitis. In the United States, a 1% strength is available over-the-counter, and a 2.5% strength is also available with a prescription. At the 2.5% strength, selenium sulfide is also used on the body to treat tinea versicolor, a type of fungal skin infection.

It can be used for adults and children over the age of 5. It should be used twice a week for the first two weeks then once a week for the next two weeks.

Selenium can cause discoloration of the hair and alter the color of hair dyes. It may also discolor metallic jewellery. It should not be used in the first 3 months of pregnancy.

Cultural references
In the 2001 film Evolution, selenium sulfide, as the active ingredient in Head & Shoulders anti-dandruff shampoo, is used to fight the alien menace, on the faulty logic that because arsenic is poisonous to carbon-based humans, selenium must be poisonous to the nitrogen-based aliens, due to their respective positions in the periodic table. However, selenium itself is toxic to humans.