Selenium Sulfide was approved for medical use in the United States at least as early as 1951. It is a chemical compound and medication used to treat pityriasis versicolor, seborrhoeic dermatitis, and dandruff. Basically, this compound works by slowing the growth of the yeast that causes the infection. Plus, it is typically applied to the affected area as a lotion or shampoo. Bear in mind that Selenium Sulfide shampoo has a few side effects such as hair loss, irritation of the skin, weakness, and feeling tired. Also remember that its use is not recommended in children less than 2–5 years old. In addition, the use of this shampoo during pregnancy or breastfeeding has not been studied. So, it’s preferable that you ask your doctor before using it. You should also take off your jewelry before using Selenium Sulfide shampoo, considering it may discolor it.