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You've probably heard someone explain that hair grows in thicker after shaving, but is there any truth to this or is it just a myth?

Hosted by: Hank Green

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Sources:

https://pdfs.semanticscholar.org/820a/e49990f0f09b97487b6a437d304cc1cee47c.pdf
https://onlinelibrary.wiley.com/doi/abs/10.1002/ar.1090370405
https://www.sciencedirect.com/science/article/pii/S0022202X15497003
https://core.ac.uk/download/pdf/82434481.pdf
https://www.bmj.com/content/335/7633/1288.full
https://www.jidonline.org/article/S0022-202X(15)47888-1/pdf
https://www.sciencedirect.com/science/article/pii/S0927776502001297
https://www.sciencedirect.com/science/article/pii/S1011134404000375
[intro].

At least once in your life, you’ve probably heard someone explain that if you start shaving somewhere new, the hair will grow back even thicker. And if you’ve ever rubbed your hand across some rough stubble after a recent shave, it’s easy to understand why.

But as far as scientists can tell, this is a total myth — even if our own experiences of battling body hair seem to say otherwise. Scientists have been looking into the connection between shaving and hair thickness since at least 1928, when a study had four men repeatedly shave a certain part of their face. That experiment, along with other early shaving studies, concluded that shaving didn’t make people more hairy.

But they only measured the rate of hair growth, and not the thickness of the individual hair shafts. So, in a later study from 1970, researchers had 5 men shave one leg every week for several months. The other leg was left ungroomed, as the control.

The team measured the diameter, density, and weight of the hair, as well as the rate of growth, and concluded that shaving didn’t make the hair grow back thicker. Other studies had similar results, like one from 2006 that analyzed high resolution photos taken with a microscope. Overall, studies consistently find that shaving doesn’t make hair grow back faster or thicker, or make new hairs grow in the shaved area.

Still, the belief that shaving thickens hair is remarkably common. Part of the reason might be that your first shaving experiences often overlap with a dramatic period of hormonal fluctuation in your life. If you began shaving regularly around puberty, your hair probably was growing in thicker.

But not because you were shaving! Another reason you might think the hair is thicker when it grows back is that over time, hair gets lighter from exposure to things like sunlight or chemical compounds. So the hair that grows back after a shave can look darker, but your cells aren’t actually making hair with more pigment.

Shaving also creates a bit of an illusion around hair shaft thickness. When you shave, you’re not pulling the whole hair shaft out of its follicle — you’re just slicing it off at the surface of your skin. It’s like a blade of grass.

When you let it grow naturally, it tapers at the end, but when you pass over it with a lawnmower, you chop it off near the base and leave a thick blunt end behind. The same thing happens with your hair. As it grows back after shaving, it feels thicker and coarser because you’ve chopped it off at its thickest point, and lost the softer tapered end in the process.

But as the hair continues to grow, wear and tear will eventually taper off the blunt end again. So while you might feel some doubt as you closely examine your stubble in the mirror a couple of days after your last shave, rest assured:. You’re not going to create a thick carpet of hair through your grooming habits.

Your body’s natural growth cycle is what’s making that call for you! Thanks to Patreon patrons Allison and Gwendolyn B for asking, and thanks to all of our patrons who suggest fascinating questions for us to answer! If you want to help support this show and get access to our patrons-only quick questions inbox, just check out patreon.com/scishow. [outro].