Is a hair detox shampoo considered a cosmetic or an OTC drug by the FDA?

It depends on label claims and active ingredients. A shampoo marketed purely for cleansing and removing buildup is a cosmetic under FDA rules. If it contains salicylic acid and makes anti-dandruff claims, it becomes an OTC drug subject to the monograph system and Drug Listing requirements. Under MoCRA, all US cosmetic facilities must also register with the FDA. Consult a regulatory expert early.