Humans have a very unique way of shedding and growing hair as compared to other mammals. Human hair growth at .3 to .4 mm a day is random and consistent, rather than seasonal like most animals. At this state, certain strands of hair are either in any of these hair stages: anagen, catagen, and telogen.

Anagen

Anagen is considered as the phase of the hair when it is most active. At this stage, the hair cells are dividing rapidly, and hair that has stopped growing, called the club hair, is pushed out by a hair new hair follicle. At this rate, hair grows at 1 cm every 28 days. It stays in this active phase, continuing to grow for six years.

The reason why some people have difficulty in growing hair is because their active phase of growth is short, whereas those with very long hair have a long active phase of growth. This is also the reason why hair on arms, legs, eyelashes, and eyebrows are short. Their active growth phase is only about 30 to 45 days.

Catagen

The catagen phase is the mid phase, or the transition of the active and the resting phases of the hair. There are 3% of your hair that is at this phase, and it only lasts for two to three weeks. At this time, hair ceases to grow and the outer root sheath shrinks and attaches itself to the root of the hair, forming a club, thus, known as a club hair.

Telogen

The resting phase of the hair is known as the telogen, and it accounts for 6 to 8% of all hairs. This phase lasts for 100 days on the scalp, but longer for hairs on the eyebrows, eyelash, arms, and legs. At this phase, the hair follicle is already at the club form, and is completely at rest. Once pulled, the hair at this phase will show a solid, hard, dry, and white material at the root. These are the hairs, amounting to 25 to 100 that normally fall out everyday.