Dermatologists care about one thing: your skin — and that extends to your scalp. Still, when it comes to the health of your scalp, dermatologist Francesca FuscoMD, says there’s no “golden rule” for how many times you should wash your hair per week — and shampooing every day isn’t necessarily “bad” for your skin.
“If a person is greasy, it’s okay to wash them every day. When it’s dry, it’s fine to wash it once a week, but at least once a week for hygiene reasons,” says Dr. fusco (She clarifies that this is because product can build up on the scalp, potentially leading to clogged pores, irritation, or dandruff.) “People with dandruff should shampoo with an anti-dandruff shampoo at least twice a week .”
TLDR; At least once a week unless you have dandruff, in which case twice a week using treatment shampoo is recommended.