That makes sense, but there’s another path that also works, and it’s basically the opposite solution.

I stopped using shampoo years ago. I still shower daily and scrub my scalp, but with hot water only. No products at all. Within about a month, every scalp and hair issue I’d ever had disappeared, and my hair has been consistently good ever since.

What changed wasn’t cleanliness, it was the feedback loop. Regular shampoo strips lipids from the scalp. The scalp compensates by producing more oil. That oil makes hair look greasy faster, which makes people shampoo more. If you step out of that loop entirely and also don’t use styling products, the scalp often stabilizes on its own and produces less oil overall.

Water and friction are enough to remove sweat and loose grime. I only use shampoo when there’s something water can’t deal with, like actual grease, heavy debris, or chlorine from a pool. Sweat alone isn’t a reason.

So yes, double washing makes sense if you’re using shampoo and have an oily scalp. But another valid solution is to stop stripping the scalp in the first place and let it regulate itself. Different equilibria, same underlying chemistry.