Moisture can soothe your scalp and calm the itch. Take a warm shower before you go to sleep every night. Wash your hair each time. Try an over-the-counter shampoo for people with psoriasis. Look for one with tar, ketoconazole, or salicylic acid. Dandruff shampoo may also help. To give it time to work, leave it on your scalp for five minutes before you rinse it out. If your doctor gave you a cream or other medicine to use during your shower, put it on your wet scalp before you shampoo. Leave it on for the prescribed period of time, then wash and rinse as usual. Always use conditioner. It will help keep your skin moist. Shampoo alone can dry our your scalp.