This information came to me via a very well respected dermatologist that I paid big money to go see while I was uninsured a few years back. He was actually enraged over the split in the hair-loss community between the real science and the quackery. He explained to me that DHT is an internal thing. It's in the blood. It cannot be "washed" away with any sort of shampoo and any claims to this notion are outright lies (according to him) perpetuated by the manufactures of some of these shampoos. The studies are not legit (he claims) and he says that the only people who don't know this are the consumers - they are the victims. The only scientifically, peer-reviewed methods of preventing hairloss are with the drug finasteride and the topical application of minoxidil.The FDA will not approve any of these shampoos regardless of their claims because the limited studies are not conclusive and what little percentage increases were shown are not substantial enough for these products to be considered a legit MPB treatment. So my advice, keep using your shampoo if you like, but don't forget to also take your fina and your foam. Do with this info what you please. I'm not up for a debate. Cheers.