The idea that hair grows faster when it's dirty is one of those myths surrounding black hair that won't go away. But while the idea of never again putting water on your hair is outrageous, there is actually some merit to this myth. So what's the truth about dirty hair and growth?
Fact: Hair needs to be cleansed, preferably on a regular basis. Never putting water on your hair is deeply unsanitary, and can lead to odor, buildup, and even dryness and breakage.
With that out of the way, it's important to address why the notion of dirty hair promoting hair growth is still so prevalent. As you probably know already, black hair doesn't require the same frequent cleansing that naturally straight hair needs. You can shampoo once a week and still easily have healthy locks. The days of believing that once-monthly washes are fine, however, are over.
Disclaimer: This "never washing" idea does not include co-washing. The co-wash process includes plenty of water, and even women who steer completely clear of traditional shampoos can have clean, healthy locks.
Part of the reason black people of yesteryear didn't shampoo as often (or go swimming) is because—prior to relaxers and even after they hit the mainstream hair care market—the main method for hair straightening was by using a hot comb. After spending several hours shampooing, drying and the hot task of straightening the hair—which can cause severe burns to the scalp and the hair with a hot comb—it's no wonder they wanted their hairstyles to last as long as possible.
Then, there are other people who just aren't as adept at caring for their mane. They wait for their stylist to cleanse and condition their hair, and if their beautician is booked solid for the next four weeks, they wait until they're available. We get it, but taking your hair into your own hands is important for its health.
One of the reasons some people believe dirty hair promotes growth is because too-frequent washing encourages dryness, brittleness and breakage—all of which happen to be some of the same issues you may face by not washing enough! If you shampoo too often (for black hair, this could be daily with a harsh, sulfate-laden cleanser), yes, your hair will absolutely dry out and break. Anyone's hair will become damaged if they shampoo every day. But the alternative (never washing) isn't suitable, either.
Natural oils, hair products, sebum from your scalp, and even air pollution all build up on your hair. Think about what happens then when you never wash it out, or only wash once a month or so. The gunk isn't helping where growth is concerned.
A clean scalp is a healthy scalp, so shampoo with a gentle product on a regular schedule, once or twice a week. All hair grows, and it grows an average of 1/4 to 1/2 inch per month, dirty or clean. That said, some women notice more growth when they cleanse their tresses and scalps more often than they did in the past. The more you moisturize your hair and scalp with water, the healthier your head will be. Hair growth flourishes from a clean, healthy scalp.
The bottom line is, dirty hair doesn't grow any faster than clean hair, so you may as well have a sweet-smelling scalp and fresh tresses. They'll look better, feel better, and be healthier, too.