Nyla Sanchez
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The Science Behind Curly Hair

— Nyla Sanchez

There are many chemical bonds, chromosomes, and genes that are responsible for the curliness of your hair. For instance, higher amounts of disulphide bonds are responsible for tighter coils and give them strength and elasticity.

Have you ever noticed how your curls tend to get frizzy on rainy or humid days? This is because moisture in the air causes hydrogen atoms inside the amino acids in your hair to bond with each other, resulting in frizzier hair. These hydrogen bonds can be broken easily when exposed to heat, through blow drying, for example.

 Hair Bonds Guide: Hydrogen, Ionic, Disulfide | Living Proof®

Ionic bonds in your hair make it stronger, though sometimes factors like a change in pH weaken and eventually break them. The covalent disulphide bonds mentioned in the introduction are the strongest and hardest to break, but they can still be broken through practices harsh on your hair like bleaching, which can change and damage the internal structure of your hair.

Your genes, passed onto you by your parents, also determine the shape of your hair. For example, different types of chromosomes, protein structures that contain a singular extract of DNA to carry genomic code from one cell to another, are responsible for whether you have curly or straight hair. The CTS, IRS, and ORS chromosomes are most relevant in this case. Additionally, curly hair is classified as a “dominant gene” trait whereas straight hair is considered a “recessive gene” trait, which means that for the most part if one parent gives you a gene associated with curly hair and one parent gives you a gene associated with straight hair, you’ll be born with curly hair. 

Moreover, those of African descent tend to have curly hair, in particular those with Sotho, Xhosa, and Zulu ethnicity. Curly hair is also found most in those with mixed ethnic backgrounds.

It’s so captivating how all curls come in different patterns due to these chemical bonds, chromosomes, genes and much more!


References

Bernard, B. A. (2003). Hair shape of curly hair. Journal of the American Academy of Dermatology, 48(6), S120–S126. https://doi.org/10.1067/mjd.2003.279

Cloete, E., Khumalo, N. P., & Ngoepe, M. N. (2019). The what, why and how of curly hair: a review. Proceedings. Mathematical, physical, and engineering sciences, 475(2231), 20190516. https://doi.org/10.1098/rspa.2019.0516

Hair Bonds 101: What They Are and How to Repair Them. Living proof. (2022, July 22). https://blog.livingproof.com/hair-bonds-guide/ 

Michelle K. Gaines, Imani Y. Page, Nolan A. Miller, Benjamin R. Greenvall, Joshua J. Medina, Duncan J. Irschick, Adeline Southard, Alexander E. Ribbe, Gregory M. Grason, and Alfred J. Crosby Accounts of Chemical Research 2023 56 (11), 1330-1339DOI: 10.1021/acs.accounts.2c00740

Understanding Curly Hair Mechanics: Fiber Strength. (2020). Journal of Investigative Dermatology, 140(1), 113–120. https://doi.org/10.1016/j.jid.2019.06.141

Westgate, G. E., Ginger, R. S., & Green, M. R. (2017). The biology and genetics of curly hair. Experimental Dermatology, 26(6), 483–490. https://doi.org/10.1111/exd.13347