Curls Week – Why does curly hair curl?

Curls Week – Why does curly hair curl?

Curls Week - Hair Romance

It’s Curls Week on Hair Romance and we’re celebrating all things curly.

Today the question is why does curly hair curl?

Hair Romance - Curls Week - why does curly hair curl

What makes curls happen and what is the difference between straight hair and curly hair?

The chemistry behind your curls

Hair Romance - why does curly hair curl

It all comes down to chemistry.

Hair is made up of proteins, mainly keratin. Your hair shaft grows from the follicle and that’s why a protein-rich diet is important for growing hair.

The protein molecules contain sulphur atoms. These sulphur atoms pair up and form a disulphide bond.

The distance between the sulphur atoms cause your hair to curl. The further apart the sulphur atoms, the more the protein molecules bend, and so the more your hair curls.

Disulphide bonds are permanent bonds, or covalent bonds. Unlike frizz caused by humidity which are hydrogen bonds. These bonds form and break more easily.

Styling your hair changes the hydrogen bonds, which is why your hair will go back to its natural state over time. Permanent chemical hair straightening treatments change the disulphide bonds, but as new hair grows the natural hair structure will come back.


Curly hair is genetic so you can thank your parents for your gorgeous curls.

The gene for curly hair is not completely dominant so if you have a mix of straight hair and curly hair genes you end up with mixed, wavy hair.

The shape of your hair follicle is determined by your genes and this is also a factor in how curly your hair is. Curly hair follicles have a hook shape which affects the shape of your hair shaft.

If you could see a cross section of a hair shaft, you would see that straight hair is round, wavy hair is oval and curly hair is flatter.

This flatter shape affects the distance between the protein molecules and the disulphide bonds, hence making your hair curly.

Does that make sense? Hope this helps to explain why your hair is curly.

What other curly hair questions would you like answered?

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