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Why is your hair curly?

Just like almost everything else about your gorge self this is down to genes (thanks mum and dad). But what other factors make our hair curly?

Whether straight or curly all hair has two major components. The shaft and follicle. The shaft are the strands that we see on our heads. The follicle is the part that lives within our scalp or dermis. These two together determine the overall shape of our hair.


The shape of our follicle is a major determinant of our hair texture. If you look at the follicle of someone with straight hair you’ll see that it’s perfectly round. However, the follicle of curly hair has an oval shape. The flatter the oval shape, the curlier the hair.

Another contributing factor is the way the follicle tunnels into the scalp. Straight hair follicles tunnel down vertically from the skin’s surface into the dermis. If the follicle angles into the dermis this will lead to a curve which will curl as it grows. It’s because of this curving that curly hair generally is drier than straight hair as the curving makes it more difficult for sebum to travel the length of the hair. So the curlier the hair, the drier it will be.


So what’s the hair shafts role in all of this? In short: protein bonding. Sorry for going all sciencey, but it has to be done:

Hair is largely made of dead cells packed full of fibrous protein known as keratin. This protein contains the amino acid cysteine which has a sulfur containing chemical group that allows it to form strong bonds with other sulfur containing molecules. As hair contains largely keratin these cysteine amino acids can bond with cysteines further down the hair shaft which contributes to the curling of the hair between the bonds. Curly hair has more of these bonds compared to straight hair as the follicle shape and angle allows different regions of the hair to come close together making these bonds easier to form.

This is how perms and relaxing treatments change the structure of our hair by taking advantage of keratin’s ability to disulfide bonds. To alter the hair from curly to straight you need chemicals that can break up or “relax” these bonds. If you go from straight to curly you need chemicals that will allow these bonds to form.

So do with these facts whatever you want – but hopefully it’ll contribute to your understanding of your curls so you can help them be the healthiest they can be. xx

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