There has been a noticeable decrease in oil production on my scalp since I starting using this. I wash my hair every other day, and usually need to use a ton of dry shampoo on my no-wash days. Since I started using this scalp exfoliant, I hardly need to use any dry shampoo. I am hoping that eventually I won't need dry shampoo at all. It doesn't tingle or burn my scalp, so it's comfortable to wear. It dries down and makes the hair crunchy, so it definitely is to be applied before shampooing, not used during the day. If I wash my hair at night, I apply a few hours before I get in the shower. If I shower in the morning, I apply before going to bed and wash out the next morning. I apply very liberally, and I think the bottle will last at least a couple of months if not longer. I will definitely be repurchasing this when I run out.