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 5.7-6.3

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



Conclusions


Hair cuticle thickness

Number of cuticle layers

Hair protein composition

Hair strength




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)



Sources:

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