The growth cycle of hair
Hair loss problems which are not inherited occur when the hair growth cycle is disrupted which can be triggered by stress, bad nutrition or metabolic imbalances. Our hair grows approximately 6 inches (15 cm) a year, depending on our race. Asian and Afro-Caribbean hair grows at slightly different rates. Afro-Caribbean hair for example, grows slightly slower at an average of 4 inches per year. As our hair grows it sheds but unlike any other mammal, the human hair cycle is random and not seasonal. At any one time a random number of hairs will be in one of three stages, anagen, catagen and telogen.
ANAGEN: This is the active stage of the hair. The cells in the root are dividing quickly, a new hair forms and pushes the “club” hair, a hair that has stopped growing, up the follicle and eventually out. During the anagen stage the hair grows approximately 1 cm every month and scalp hair stays in this active stage of growth for 2 to 6 years. Some people are known to be unable to grow their hair past a certain length, this is because they have a short active phase of growth and those who can grow their hair very long have a long active phase of growth. The hair on the rest of our body, i.e. our eyebrows, lashes, arm hair, has a very short active growth phase which is why they are much shorter than the hair on our scalps. When the anagen stage is cut short, lots of hairs enter the telogen hair loss cycle at the same time and you may see more hair loss than normal.
CATAGEN: This is a short transitional stage which approximately 3% of all hairs are in at any one time. This stage lasts for 2 to 3 weeks and no pigment is produced. Growth stops, the outer root sheath shrinks to about ⅙ of it’s original size and attaches to the root of the hair. This is what creates a “club” hair.
TELOGEN: This is the resting stage of the hair life cycle and accounts for 8-14% of all hairs on the scalp. This stage will last for approximately 100 days for scalp hairs and longer for eyebrows, eyelashes, arm and leg hair. These hairs account for those hairs you lose when washing or combing your hair. In this stage, the hair follicle is at rest and the “club” hair has been completely formed. If you pull out a hair in this stage you will notice a solid, dry, white material at the root of the hair. In this stage about 25 - 100 telogen hairs are shed each day. At the end of the telogen stage the follicle is inactive for about 3 months then re-enters the anagen stage and the hair cycle starts all over again. Each hair follicle is independant and goes through the growth cycle at different times, otherwise all your hair would fall out at once.