When shopping for a new shampoo, you likely start by standing in the aisle and staring at the dizzying array of options. Do you want a clarifying shampoo to remove build-up? A purple shampoo to cut brass? Once you’re thoroughly overwhelmed by the choices, you’ll probably resort to grabbing bottles off the shelf until you find the one that smells the best. While that buying practice may work for most, if you’ve been noticing your scalp looking flaky, itchy, or red, that beloved fragrance may be to blame.

“Most shampoos contain fragrance, and fragrance is the number one cause of allergic contact dermatitis,” says Peterson Pierre, M.D., dermatologist and founder of the Pierre Skin Care Institute. (FYI: Allergic contact dermatitis is a reaction resulting from contact with a substance or an allergy to it, according to the Mayo Clinic.) Similarly to how fragrance can irritate the skin on your face, it can also cause a reaction on the skin of your scalp. The symptoms for contact dermatitis could be redness, itching, or rash, says Trang Vu, a cosmetic sciences researcher and Ph.D. candidate at the University of Cincinnati.

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