Hair Biochemistry and Its Process
                     Hair Biochemistry 
and Its Process
INTRODUCTION
Hair is far more complex than it appears on the surface. We all know that it not only plays a vital 
role in the appearance of both men and women, but it also helps to transmit sensory information 
as well as create gender identification.
Source: www.webmd.com
Hair Follicles
Hair has two distinct structures - first, the follicle itself, which resides in the skin, and second, the 
shaft, which is what is visible above the scalp.
Source: www.webmd.com
Hair Shafts
The hair shaft is made of a hard protein called keratin and is made in three layers. This protein is 
actually dead, so the hair that you see is not a living structure. 
Source: www.webmd.com
Hair Growth Cycle
Hair on the scalp grows about .3 to .4 mm/day or about 6 inches per year. Unlike other 
mammals, human hair growth and shedding is random and not seasonal or cyclical. At any given 
time, a random number of hairs will be in one of three stages of growth and shedding: anagen, 
catagen, and telogen.
Source: www.webmd.com
Anagen
Anagen is the active phase of the hair. The cells in the root of the hair are dividing rapidly. A new 
hair is formed and pushes the club hair (a hair that has stopped growing or is no longer in the 
anagen phase) up the follicle and eventually out.
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Catagen
The catagen phase is a transitional stage and about 3% of all hairs are in this phase at any time. 
This phase lasts for about two to three weeks. Growth stops and the outer root sheath shrinks 
and attaches to the root of the hair. This is the formation of what is known as a club hair.
Source: www.webmd.com
Telogen
Telogen is the resting phase and usually accounts for 6% to 8% of all hairs. This phase lasts for 
about 100 days for hairs on the scalp and longer for hairs on the eyebrow, eyelash, arm, and leg.
Source: www.webmd.com
The Process
The human hair follicle cycles in active growth and resting phases controlled by a 
complex network of biochemical processes, yet to be fully understood. It is well known 
that hair follicles on scalp respond to androgens by a shortening of the anagen growth 
phase causing hairs to regress to a finer, thinner texture. 
Source: pubmed.ncbi.nlm.nih.gov
The Process Cont.
 Kinetic constants have been evaluated for several enzymes which mediate 
dihydrotestosterone formation, including 5a-reductase, and the cytochrome P-450 
aromatase enzyme in isolated human hair follicles and sebaceous glands from scalp of 
men and women with androgenetic alopecia.
Source: pubmed.ncbi.nlm.nih.gov
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