Rarely, people may have an allergic reaction to selenium sulfide, causing symptoms that include hives, swelling in the face or throat, and difficulty breathing. If this happens, get emergency medical help right away. It is rare, but some people may experience skin irritation while using selenium sulfide. These symptoms may include dryness, blistering, peeling, redness, itchiness, or other irritation. Other side effects include mild dryness or oiliness of the scalp, or an increase in normal hair loss. If you have any side effects that are bothering you or will not go away, talk to your doctor.