Head & Shoulders Clinical Strength 400ml is a powerful, over-the-counter anti-dandruff shampoo sold in the USA. Its key active ingredient is 1% Selenium Sulfide, a potent antifungal agent. This formula is designed to provide prescription-strength relief for severe dandruff and seborrheic dermatitis, addressing symptoms such as flaking, itching, irritation, and redness. It is clinically proven to fight the root cause of dandruff and is often available in different variants, such as "Intensive Itch Relief" or "Dry Scalp Rescue," to target specific scalp concerns.