Curls Week – Why does curly hair curl?

by Hair Romance on July 10, 2014 · 5 comments

in Curly Hair

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.

Genetics

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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{ 4 comments… read them below or add one }

Caitlin July 10, 2014 at 8:48 am

I had dead straight hair until I was about 18. Over the past 8 years it started to get wavy in the back section and today at 27 I have wavy hair around my face and full on curls at the back. Hairdressers find my hair mysterious!

Reply

Hair Romance July 10, 2014 at 10:24 am

Hi Caitlin, my hair totally changed too! So weird. It’s usually hormones that create this change. We know hormones (especially androgen and thyroid hormones) change your hair but it’s not exactly clear how the shape of the hair changes. One theory is that these hormones also change your muscle tone. This includes your scalp and this change surrounding the hair follicles could cause them to change shape (become rounder or flatter) and hence make your hair curly or straight. It’s not proven but it’s the theory that makes the most sense from all that I’ve read. Hope this helps! Christina x

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Isa July 30, 2014 at 11:17 pm

I had the most beutiful and defined curls ever!! and 3 years ago my hair began to change… i am 25 now… i miss my curls… now i have wavy hair with some undefined curles here and there…. i would love to have my natural curls back :’(

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Annette August 25, 2014 at 9:33 pm

Hi Isa, exact same thing has happened to me. I’m a lot older than you (!) but basically after some perms as a teenager, my hair became naturally curly! and has gone through various degrees of curliness since my teens. My hair became super curly from about aged 28 onwards and stayed like that until approximately 3-and-a-half years ago (I’m 40 now). Like you, I have wavy hair with undefined curls now and I miss my telephone-wire curls so so much and sadly nothing I have tried has brought them back. I moved house about 3-and-a-half years ago and so I thought that the loss of curl had something to do with different water! but it doesn’t seem so as I still have access to the water supply where I used to live (at my mum’s) & have tried washing it there to see if it would help & it hasn’t :( I can only assume my hormones have changed or something!, or maybe it’s due to years of over-processing as I do colour my hair, though, during it’s curliest periods I was continuously colouring my hair too and so I don’t know why all of a sudden one day my curls just died! If you come up with any miracle curl revival, please let me know, as I will you! Thanks!

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