Hair: Does it matter if you are Black, White or Asian?

In the first installment, we looked at physical hair properties and ethnicity. Here is the rest of the compilation!

1. Hair thickness

I previously discussed hair shape and a question arose on hair thickness so here are the figures. The figures do not give the diameter of the hair but rather the area. This is because hair is usually not perfectly round and has several diameters some short, some long. (For easy reading I rounded off the numbers  to the nearest hundred)

Asian Hair Caucasian Hair African Hair
Area of cross sectional cut (see image above)

4600-5000 3700-4000 4100-4500

2. Hair growth rate

Hair growth is a contenious subject since there really is only one study for African hair (whose result gave a much reduced growth rate). However the figures are valid for that study and show a much reduced growth rate compared to Asian or Caucasian Hair.

African Hair Asian Hair Caucasian Hair
Hair growth rate (per year)

3.7-4.3 inches 6.3 inches 5.8 inches
5 inches

3. Hair Protein Composition

There used to be theories that curly hair
1. Gets its curl from having more of certain amino acids which allow it to twist
2. Is brittle because the hair lacks strengthening amino acids

Both of these theories have been proven to be wrong since hair across the races is made up of very similar quantities of amino acids.

3. Hair Strength
Hair strength studies are another contentious subject. There have been four independent tests in different labs. The results

1. Two labs showed that African hair is slightly weaker than Asian or Caucasian Hair. Asian and Caucasian Hair had similar strength.
2. Two labs showed that all hair regardless of race had similar strength

Key Similarities
Hair cuticle thickness
Number of cuticle layers
Hair protein composition
Hair strength

Key Differences
Hair Shape
Hair thickness (order of thickness- As,Af,Ca)
Hair growth rates (As and Ca faster than Af)
Hair Colour (not discussed here but widely known)

Experimental Dermatology, 14: 311–314, 2005
Journal of the Society of Cosmetic Chemists, pg 155-75, 1978
J. Soc. Cosmet. Chem., 22, 839-850, 1971
International Journal of Dermatology ,45, 1435–1437,2006 
Dermatologic Therapy, Volume 17, Number 2,  pp. 164-176(13), 2004
Br J Dermatol, pg 294-7, 2001
J Am Acad Dermatol, 46,6, S115-119, 2003
J Dermatol : 15: 393–396 , 1988
J Dermatol : 17: 62–64.,1990
EXS : 78: 149–175,1997


  1. Really interesting JC - would Af hair grow slower because it is weaker or because of the oval/eliptical shape (interesting that it's the thickest too)(CHM)

  2. Hmmm... maybe I haven't done enough research but those differences seem quite significant to me. Doesn't the shape of the hair have important effects in how the hair behaves and responds to products/handling?

  3. CHM- I am not convinced on the growth rate actually. While the study is valid it was only based on 35 individuals. I would love it to be expanded and done at different time points in the year similar to the way Caucasian studies have been done.

    Nicki - I have not seen any single study that says the shape of the hair shaft affects how a product behaves. It is the condition of the shaft that appears to be of great importance meaning
    1. how many cuticle layers are present?
    2. has the cuticle been disturbed by bleaching or relaxing

    The presence of a cuticle and the condition of it are the two main factors as to whether a product will have an effect or not.

    I do think the shape of the hair is important because it can impact how the cuticle fails. The elliptical shape would probably make it easier for the cuticle to separate away especially under force or when chemically processed (relaxing or bleaching which raise the cuticle).

    To be honest, most hair products are designed to just sit on hair. Unless hair is damaged most substances are too large to get past the cuticle. The exceptions are water, some oils like coconut and olive oil and some very small proteins.

  4. Jc - This is fascinating to me! Thanks for putting it all together so neatly.

  5. Is the Caucasian hair in the study straight and of those people who are socially white? I am just a little confused because medium to super curly hair is oval - regardless of race/ethnicity. And I guess those of us from generationally mixed backgrounds would just fit somewhere in the middle of two or three of the groups?

  6. Mara not sure what you mean by 'socially white'. The studies I have sited have a mix of Caucasian hair including straight, wavy, curly and different hair colour auburn (brown and red) and blonde.

    Caucasian hair is slightly oval but not as elliptical as African hair.

    When it comes to mixed heritage, there is no fixed rule, some people will have hair more like one parent than the other and others will have something in between. Hair is very much individual

  7. The study you found was looking at hair growth...does it tell you what state or condition African American hair was at the time the study was being done. Was is relaxed or was it natural? Were they were extensions/wigs/braids or wearing the hair naturally out.

    I may be biased in saying this but African Americans do alot to our hair especially since our hair the kinkiest of all races and its really now that we are learning how to really take care of hair or retain hair growth through today's information sharing technologies, ie YOUTUBE.

    How did the study determine African American hair has less hair growth than the other groups? Were men involved in the study? I remember you posted something in the past normally men grow hair faster than woman due to testosterone (may be wrong on that).

    Can you clarify this?

  8. Hello,

    First time commenting here! I am transitioning and less than 7 mnths into my journey I had 3.5 inches of growth so it seems that the yearly avg. of 6"-found on various sites on the net, is spot on.. I'm not mixed ( more mixed than the avg. Jamaican) so the rate of my growth is not abnormal for a person of African descent.

  9. I have always had the feeling that when I run the individual strands of my hair through my fingers, they would feel more or less "flat" and not round. I have different hair types on my head, and especially the "zigzag" ;) parts would feel different than the wavier ones. It has been a mystery to me my whole life. Now I know why! Thank you!
    (PS - white curly here, for the statistics ;))

  10. Hi there,

    I'm asian woman. My hair grows about 20 cm per year. Am I abnormal? it isn't impossible, is it? My hair's volume is also thick according to some info I've found. It's about 13cm around my pony (without some frontbang) and I only trim my hair once, max. twice a year but I have almost no split ends at all. All of these are really contradiction to info I've found. I'm just wondering is there anybody out there like me or I'm just the black sheep...

  11. The shapes of different types of hair are just generalities that apply to the straight vs. curly continuum rather than strictly by ethnicity (although some ethnicities tend to have curlier or straighter hair than others, especially those of asian or african descent). I am a woman of Irish-German-Jewish descent with 3c (very curly) hair and my hair is shaped like the one on the right (flattened), as is all really curly hair.


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