Dermatologists are concerned about one thing: your skin — and that extends to your scalp. Still, when it comes to your scalp health, dermatologist Francesca Fusco, MD, says there is no “golden rule” for the amount of times you should wash your hair a week — and it’s not necessarily “bad” for your skin to shampoo every day.
“If a person is oily, it’s fine to wash it every day. If they are dry, it’s fine to wash it once a week, but once a week at least for hygienic purposes,” Dr. Fusco says. (She clarifies that this is because product can build up on the scalp, potentially leading to clogged pores, irritation, or flakes.) “Individuals with dandruff should shampoo at least twice a week using an antidandruff shampoo.”
TLDR; Once a week at minimum, unless you have dandruff, in which case twice a week with treatment shampoo is recommended.