PRE-SHAMPOO PURIFYING MASK- POLLUTED SCALP AND HAIR. Our increasingly intense lifestyles are suffocating our hair and scalp. Pollution, stress, cigarette smoke, product accumulation, hard water? A hair detox is much needed. The 1st step of a HAIR DETOX routine is a pre-shampoo a Ghassoul mask that absorbs impurities that suffocate the scalp (pollution, dust, limescale, product residue, etc).