Youthology leaves a nasty white residue. I did not like the product, and have attempted to return it repeatedly. They do not answer the ohone number provided, they simply leave you on hold for over an hour (absolutely no exageration, try calling and see for yourself) Once they get your credit card, they will continue to charge it, regardless of how many times you email them. (reaching by phone is impossible) The product is CRAP. Does not work as advertised, and they do not honor their return policy. read full review »