Washing your hair is a crucial part of any grooming routine. But since everyone's hair is different, there's no one-size-fits-all hair-washing rule. Some people use shampoo and conditioner daily, while others prefer to lather up a couple of times a week. Is one strategy better than the other?
Having healthy hair — strands that feel well-hydrated and don't break easily — "is really a reflection of both the scalp environment and the hair shaft integrity," says Dr. Kseniya Kobets, director of cosmetic dermatology at Montefiore Einstein Advanced Care in Elmsford, New York. Your scalp shouldn't be itchy, red, flaky, extra oily, or feel dry or painful, Kobets says. "I always tell patients: if your scalp is calm and balanced, your hair is much more likely to behave."
"The ideal interval between hair washing actually has to do with your scalp more than your hair," says Dr. Carolyn Goh, a dermatologist at UCLA Health, who specializes in hair loss and scalp disorders. The scalp sets the baseline, she explains, and the hair decides how far that interval can stretch. "The reason to go longer between hair washings has to do with the hair and how dry it can get from frequent washings."
The oils from your scalp "act as a natural moisturizer, keeping your hair and scalp from getting overly dry," says cosmetic dermatologist Dr. Danny Guo, who's based in Calgary, Canada. However, some people produce more oil than others, and excess oil can make your hair greasy, Guo adds. Washing your hair removes oil, dead skin cells, hair products, and dirt — all of which can build up on your scalp, Kobets says.
The American Academy of Dermatology recommends washing your hair based on "how often it gets dirty or oily." For most people, that usually means every two to four days, but it can mean daily for people with oily scalps or every week or two for those with dry or curly hair, Kobets adds. This is because oil may more easily travel down the length of your strands when you have straight hair, but this may not happen with curly hair, sometimes making it drier and more prone to breakage, Goh adds. "For the average person, washing your hair two to three times per week is ideal," Guo says.
Overwashing your hair may cause it to become dry and brittle or break easily, Goh says. And your scalp may feel tight, itchy, or irritated, says Kobets. When you don't wash your hair often enough, it'll likely look and feel greasy and might smell bad, Guo says, and your scalp might be flaky and itchy. "If you feel like you need to use some dry shampoo to soak up the oils on your hair, you probably need to just wash in the shower with actual shampoo," Goh adds.
Which shampoo and conditioner to use also depends on "what your scalp is telling you," not hair type alone, Kobets says. Shampoos labeled "clarifying" are recommended for oily hair and scalps, and hydrating, gentle shampoos are better if your scalp is dry, Guo says. Sulfate-free shampoos, which tend to be gentler and don't strip away oils, work well for curlier or drier hair, Goh adds. High-sulfate products, on the other hand, can be "too stripping" if used frequently, says Kobets. "It's not that these ingredients are universally 'bad,'" she says. "It's about matching the formula to your scalp tolerance."
Most people benefit from using conditioner after shampooing, Goh says. It can help restore some of the natural oils that were stripped away after washing, and it can improve the hair's texture and appearance while detangling it, adds Guo.
People tend to use too much shampoo, Kobets says, and she suggests about a quarter-sized amount, which is usually enough for the scalp and roots. Her approach is to apply it to the roots, massage it into the scalp gently, and let "the lather cleanse the lengths as it rinses," then rinse it out completely. Over-scrubbing can irritate the scalp, she adds.
How much conditioner to use depends on how much hair you have, Goh says, and she suggests applying it to the ends and shaft rather than the scalp, unless the scalp is particularly dry, then rinsing thoroughly. Lukewarm water is best for the skin and hair, Guo says, because hot water can irritate the scalp by stripping oils and causing dryness.
Overall, healthy hair depends on a healthy scalp, Kobets says. "The biggest misconception is that it's about how often you wash, when in reality, it's about whether your routine and ingredients match your scalp and hair biology."