The frequency at which you should shampoo your hair is a mysterious and mercurial science. I’ve heard advice ranging from “wash in the morning and at night,” to, “wash once a month and use hair oil the other 29 days.” So what are some things that happen when you wash your hair too much, or too little? As someone with curly, fine hair, there seems to be some kind of delicate balance of shampooing I’m supposed to maintain, and if I get it wrong, my hair can easily get too dry or too greasy (there’s got to be a Goldilocksmiddle ground here). My scalp is sensitive too: it gets itchy, red, flaky, and oily if I’m not careful. I talked to Dr. Jeff Donovan, a Canadian dermatologist who specializes in hair loss and health, and it turns out the answer is more nuanced than I thought.
Dr. Donovan stresses the importance of tailoring your habits to your specific hair type, saying, “This is not a simple question because what constitutes 'too often' is different for everyone!” So what are the different hair types? It doesn’t boil down just to “straight” or “curly.” There’s a wide range of hair types, from the follicle to the thickness and texture of each strand. I looked on the Curl Centric website, which provided a thorough though perhaps not conclusive list of hair types. First of all, note the thickness of your individual strands: How can you tell the difference between fine, medium, or coarse hair? You can test it by feeling an individual strand to check it for thickness. Then note the general texture of your hair (such as straight, wavy, curly, and natural). Hair types are more of a spectrum than a set of distinct categories, so you may find you fall in between hair textures or strand types, and you may have a mixture of different types.