It does penetrate the skin. This isn’t even debatable. It does reduce some systemic DHT. But, for me, and others. The DHT reduction isn’t enough to cause side effects. For me, the dutasteride is strong enough to stop my hair loss and even reverse it a little, but it trickles so slowly into my system I don’t get the dump in my DHT. I believe that’s the culprit for most side effects. That’s my theory.