For seborrheic dermatitis and dandruff, several highly effective medicated shampoos can help. Look for over-the-counter options containing generic active ingredients like ketoconazole, selenium sulfide, or zinc pyrithione, which target the yeast responsible for these conditions. Shampoos with salicylic acid or coal tar are also great for removing stubborn scales. To use them, gently massage the shampoo into your scalp, leave it on for 3 to 5 minutes to let it work, and then rinse thoroughly. Use these 2 to 3 times a week. If your symptoms persist, a doctor can prescribe stronger treatments like topical ciclopirox or mild steroid solutions.