Hair is made up of a protein known as keratin. Individual hair strands grow from the follicle, or root, situated under the skin. Active cells inside the root divide and grow to become hair strands. Blood vessels ‘feed’ the hair follicles by offering the essential nourishment. The blood vessels also supply the follicles with hormones which stimulate and regulate hair growth.
As the hair grows, it passes through four distinct stages: anagen, catagen, telogen, and exogen. It then matures up and falls out years later. The hair growth occurs at an average rate of a quarter to half an inch every month. At any given time, different strands are at different stages of growth.
The following is an in-depth exploration of the four distinct stages of hair growth:
Anagen (Growth) Phase
This is the active growth phase which can last from two to seven years. This stage determines the length of your hair. 85-90% of your hair is in a growing phase at any given time.
Catagen (Transitional) Phase
This is a transitional phase that occurs at the end of the anagen phase. This form of transition lasts for 10 days. At this time, the hair strands shrink and detach from the dermal papilla. At any given time, almost 3% of your hair is in this phase.
Telogen (Resting) Phase
This phase lasts for about three months, and during this stage, hair follicles undergo zero growth. As the older hair rests, new hair begins to grow inside the root. About 6-8% of your hair is in this phase at any time.
Exogen (Shedding) Phase
When the telogen phase ends, the old hair detaches from the skin as the new hair continues to grow. You may shed about of 50-100 hairs each day through this natural process.
If any disruption occurs during any of the stages, you might experience hair loss or thinning. Disruptions are triggered by conditions like metabolic imbalances, illness, or poor nutrition. During a disruption, or when a hair follicle is damaged, hair falls out faster than it is regenerated. This causes the formation of a patchy section on your head, a receding hairline, or overall hair thinning.