Most of us will do just about anything to avoid the dreaded “bad hair day.” But despite our mutual love for our hair, we’re still divided on one essential grooming rule: How often should we wash it? Some boast that less is more when it comes to shampoo, while others claim a daily wash is the reason they have such luscious locks. The real answer, however, is largely dependent on your personal hair texture, activity level, and the kind of look you’re aiming for.

What Is Shampoo Anyway?

When it comes to hair washing, Americans are at the top of the game, according to a survey conducted by Procter & Gamble. The consumer goods company found Americans shampooed on average 4.9 times a week — twice as often as Italians and Spaniards. What’s more, 40 percent of American women report shampooing on a daily basis.

The main reason we use shampoo is to get rid of the build-up of oil and dirt that develops when we forgo shampoo for too long. This grease is actually the buildup of a natural oil known as sebum, which is secreted from the sebaceous glands found throughout the skin’s surface. Sebum plays a vital role by creating a waterproof oily seal on our skin and hair, which protects and strengthens. Although it is both natural and necessary, too much sebum can cause side effects like acne and make hair sticky, which causes it to not only stick together but also more likely to catch dust and dirt in the environment.

Shampoo contains a detergent — not much different from that found in dishwashing liquid or bath gel — which works to clean away sebum buildup. The detergents coat the dirt and oil, separating them from the hair strands. All of it then gets washed off when you rinse out your hair.

But while everyone produces the same amount of sebum, different hair types and textures can change the way the sebum works. For example, in people with fine, straight hair, larger amounts of sebum can move down their hair’s shaft, making it look stringy and causing it to stick together more quickly. Twisted strands of wavy and curly hair prevent large amounts of sebum from traveling down the shaft, causing the hair to be dryer and more prone to damage, the Huffington Post reported.

Due to these differences in hair types, stylists recommend shampooing curly and wavy hair less often than straight, fine hair to prevent it from drying out too much, GQ reported. Afro hair, with its tightly coiled strands, needs the least amount of washing. On the other hand, those with straight hair who prefer it to be dry and light should wash their hair every day.

People who exercise often or sweat heavily may also want to wash their hair on a daily basis. Frequent washing may also benefit those with very oily or very dry scalps, even if that goes against conventional wisdom. “If you have oily scalp, then daily washing is needed,” Dr. Carolyn Goh, assistant clinical professor of medicine at the David Geffen School of Medicine at UCLA, told WebMD. “Sometimes people think they have dry scalp because they have dandruff, but in those situations, more frequent washing is also helpful.”

Giving It Up For Good

While it’s inevitable that hair will get greasy after an extended period without shampoo, the scalp will eventually be able to “self-clean.” Despite mostly anecdotal evidence suggesting self-cleaning hair is real, the idea is that the scalp will eventually return to its natural balance of sebum production — in which just enough sebum is produced to protect the hair from damage, but not enough to make it greasy. In addition, the sebum creates a barrier between the strands of hair and the outside world, theoretically preventing any dirt or grime from getting inside. Those who follow this “anti-shampoo movement” claim that without shampoo, their hair is stronger and fuller than ever before.

Greasy hair, however, is not the only side effect of giving up shampoo. According to The Telegraph, hair also begins to produce an unpleasant smell when left unwashed for too long. The buildup of oil and skin cells caused by infrequent washing can also lead to a number of health conditions like dry, flaky dandruff. Inflammation and irritation from scalp problems or clogged pores caused by buildup can affect the quality of the hair and increases risk of thinning or hair loss. Dr. Susan Lin, founder of MD Lash Factor, told Medical Daily that about 25 percent of hair loss is due to scalp issues.

Of course, not every case of dandruff is caused by sebum buildup, and not all who forgo washing will develop this condition. When it comes down to it, experts are just as clueless as we are over exactly how often (if ever) we should wash our hair. Maybe, it’s simply best to go with what works for you.