Selenium sulfide shampoo is a medicated shampoo primarily used to treat dandruff and seborrheic dermatitis. It works by reducing the production of natural oils in the scalp and slowing the growth of yeast that can cause flaking and itching. This shampoo is also used to treat tinea versicolor, a fungal infection that causes discolored patches on the skin. Regular use of selenium sulfide shampoo helps to control scalp conditions, alleviate symptoms, and maintain a healthy scalp environment.