An anti-dandruff shampoo contains active ingredients such as salicylic acid, ketoconazole, selenium sulfide, tar, and pyrithione zinc, which are known to have antibacterial, antiseptic, and antibiotic action. They help prevent the microbes from thriving on the scalp. Another advantage is that they prevent dead skin from building up on the scalp, which causes white or yellow flakes on the scalp. Applying these products to your dry skin on the scalp can prevent the clumping of dry skin.