About 90% of Americans shampoo daily. One hundred years ago, people only washed their hair monthly, and in the 1950s, it was customary for women to have their hair washed and set once a week at the salon.
Related: Eight Things Your Hair Says About Your Health
A clean head of hair feels fresh and smells great but over-washing can turn one's healthy locks into a pile of straw. The average person's hair grows less than half an inch per month so long strands that have been subjected to a lot of shampooing (as well as chemical treatments, blow drying, and the elements), tend to get dried out and dull at the ends and even break off. Dirtier hair-gasp-also holds a style better.
How often you need to shampoo depends on how oily your scalp is and your hair's texture. Oil-known as sebum-travels more easily down smooth, straight hair, making it look greasier faster. Sounds a little gross, but sebum helps moisturize and waterproof the hair shaft. This is one reason why curly or coarse hair is drier. When you wash every day, you typically strip off this natural moisturizer and then have to slather it back on in the form of commercial conditioner.
Joe Murray, owner of Hale Organic Salon in New York City, tells Yahoo! Shine that shampooing a couple of times a week is plenty. "If you can't stand a being a little oily, then coat your wet hair with conditioner up to the ears to protect it and then just wash the scalp." On gym days, try simply rinsing with water instead of shampooing and finish with a light conditioner to detangle. Another tip Murray offers is to "spot clean around the hairline with a little dry shampoo. It will also help stretch the time between blow outs."
Shampooing does stimulate the scalp, which brings blood flow and healthy nutrients to the hair follicles. As an alternative, Murray is a fan of a gentle daily scalp massage and regular brushing with a good quality hairbrush.
People with flaky scalps may be inclined to shampoo frequently, but dermatologist and spokesperson for the American Academy of Dermatology, Nia Terezakis, MD says this can actually exacerbate the problem. "When you have a flaky scalp its not dirty, its dandruff or a form of psoriasis," she explains to Yahoo! Shine. "Use a shampoo formulated for dandruff and let it sit on your scalp for 20 seconds before rinsing." You can follow up with a separate shampoo and conditioner of your choice, "But don't scrub," she advises. "It will flake even more."
When you choose a shampoo, Terezakis says to pick a product that is made for your specific hair type whether it be oily, dry, limp, curly, etc. "Companies spend a lot of money on cosmetic chemists and different products really do work." One exception: "Baby shampoos aren't necessarily gentle on adult hair," she warns. "They are made because babies squirm. They don't sting the eyes but they can be drying."
If you are used to washing your hair daily, it can take a few weeks to get used to a new routine. You may be over producing sebum to compensate for stripping the scalp. Gradually increase the days between shampooing and see if your hair becomes healthier and takes more time to appear dirty as a result.