No, dirty hair does not grow faster because your hair grows beneath your skin where the elements that cause dirty hair like sebum, pollution, and toxins cannot reach it. Hair cells are dead once they pass through your scalp to where dirt reaches them, and dead cells cannot reproduce or grow, which means the dirt cannot impact how fast your hair grows.
But dirty hair can make you lose hair faster by causing stress, inflammation, and even prematurely aging your scalp.
Why Dirty Hair Can’t Make Hair Grow Faster
Healthy hair grows half an inch per month (about 6 inches per year), but because all of the growth happens beneath the scalp, there is no way for dirt to make it grow any faster. This is because hair grows out from the hair follicle that lies beneath the skin (your scalp), and as it grows it pushes the rest of the hair strand out.
Because all of the growth occurs below the skin, there’s no way dirty hair could grow faster since the hair you can see, touch, and choose not to shampoo isn’t actually the part that’s growing. But dirty hair doesn’t make it grow faster, it can make it grow more slowly, and even lead to premature hair loss.
How Dirty Hair Hurts Hair Growth
Bad hygiene can foster the perfect environment on your scalp to breed fungus, bacteria, and can create “oxidative stress”. Oxidative stress can negatively affect your hair before it sees the light of day, ultimately leading to premature hair loss according to this article at the NIH.
Dirty hair comes from a combination of your body’s natural lubricant called sebum mixing with all the stuff you encounter on a daily basis including dirt, toxins and chemicals. There's also the pollutants in the air. These attach to dead skin cells and combine with both the sebum and the products you use on your hair for styling.
As these elements mix together, they create buildup on your scalp, which then oxidizes (i.e. chemically reacts with oxygen) to provide the breeding grounds for fungus and bacteria. Then we get to the last step which is inflammation and oxidative stress.
Oxidative stress means that your body won’t be able to detoxify your ability to undo the damage caused by the pollutants, products, and toxins you encountered on a daily basis.
This oxidative stress caused by dirty hair ages your skin (i.e. your scalp) faster, and premature aging can make you go gray more quickly. It can also lead to your hair thinning sooner and possibly cause it to stop growing all together. And oxidative stress can slow hair growth according to this other study at the NIH.
40 might be the new 20, but if you believe the myth about dirty hair growing faster than 40 will be the new 60. So don’t skip the shampoo, and make sure to wash with the right frequency for your hair needs. This is dependent on if you live in a city with more pollution, the tools and products used for styling, and if you have an active or sedentary life.
Now you know the facts behind the myth that dirty hair grows faster, and how you can keep your hair growing at the optimal rates. If you want to learn the truth about other hair myths, subscribe to the TELETIMES blog below.