Posted this in the Blood, Hair and Saliva Forum, just thought I would bring it over here. From NORML website: DRUG SCREENS? It has been suggested that the ingestion of certain substances might alter body chemistry so as to disguise drug use. Although many products are currently being marketed as drug screens in head shops, High Times ads, etc., few have any solid scientific basis. Activated charcoal, a common detoxifier, might help lower metabolite levels a bit in long-term users if taken over the course of some days or weeks. It has been suggested on theoretical grounds that lecithin, a food emulsifier, might also be useful if taken over extended periods, but this hasn't been proven. A number of high-priced herbal teas and powders are promoted as urine cleansers, with no good medical rationale. While some users have reported remarkable success with them, many others have not. Independent experiments suggest that it may be water dilution, not the screen itself, that accounts for success. Different likes for different tykes it would seem.