It doesn’t know. That’s stupid. I assume if it’s cleared by shampoo then it has an easier time excreting more. It could also be that shampoo causes it to produce more in some way chemically, or that the oil shielded it from something that causes it to produce more. I don’t know the mechanics of it, and I don’t think there’s been any research into it. All I can say is that my scalp seems to have stopped producing as much oil when I changed how I clean my hair.

I’ve seen one person post one article saying it isn’t real. I read it. It doesn’t have any research behind it. It only makes claims like the glands not having sensors. Sure, but many parts of our body perform differently based on different circumstances without sensors. To dismiss all the people with experience with no experience or evidence is pretty short-sighted. I’m sure that doctor is intelligent and knows her stuff to some extent, but she overreached with her conclusion without doing any analysis.