The purpose of the deep-cleansing shampoo is to remove styling product residue, excess fat, dirt, and other impurities from the scalp. Its washing ingredients are more substantial, i.e., high pH, than treatment shampoos, and usually do not contain conditioning ingredients. I recommend using a deep cleansing shampoo once a month or less often. In too many uses, it can turn the scalp's average flora production, i.e., the skin's protective layer on its head, and the hair starts to get even greasy because the scalp dries out. But don't use a deep cleansing shampoo when you have scalp problems, not the scalp.