Selsun is a medicated shampoo used to treat dandruff and seborrhoeic dermatitis. It works against dandruff in two ways; by reducing greasiness of the scalp and by slowing down growth of the layer of skin cells on the scalp that cause dandruff.

Selsun contains the antifungal selenium sulphide which is used primarily to control scalp disorders. It kills the fungi that cause the inflammation, flaking and itching associated with such conditions. Selenium sulphide can also be used to treat pityriasis versicolor, a fungal infection of the skin.