Anagen (Hair Growth) Phase
The anagen, or growing, phase is the first part of the hair growth cycle. During this phase, cells of the bulb divide rapidly, resulting in new hair growth. Eighty to 90% of hair follicles are in the anagen phase at any given time. The anagen phase lasts somewhere between two and seven years. The length of the anagen phase determines the maximum hair length. For example, people who have very long hair have a very long anagen phase. There are many factors that influence the length of the anagen phase, including genetics, nutrition, age and overall health.
Catagen (Transition) Phase
After the hair growth phase enters the catagen phase. This short, transitional phase only lasts two to three weeks. During the catagen phase, the hair stops growing and detaches itself from the blood supply. The hair becomes what is known as a club hair.
Telogen (Resting) Phase
The telogen, or resting, phase follows the catagen phase. During the telogen phase, the club hair rests while a new hair begins to grow beneath it. This new hair will eventually take the place of the club hair. The telogen phase lasts for three months, and 10-15% of all hairs are in this phase at any one time.
Exogen (Hair Shedding) Phase
The exogen, or hair shedding, phase is the last part of the hair cycle. During the exogen phase, the resting club hair detaches and falls out. Every hair eventually sheds, and it’s completely normal to lose 50 to 100 hairs each day.
In fact, the exogen phase is why you’ll frequently see hairs in your shower drain or on your hair brush. You should only be concerned if there’s a sudden change and many more hairs than usual are falling out.
After the exogen phase, the follicle then returns to the anagen phase and the cycle repeats.
Hair shedding is a natural and necessary part of the hair growth cycle. However, excessive shedding can occur for a variety of reasons. Many types of hair loss happen when more follicles than normal go from anagen phase to the catagen phase. When these hairs reach the exogen phase and fall out, hair will appear thinner.
Thickness of hair
How much hair you have on your body and head is also determined by your genes. Nearly everyone has some hair loss with aging. The rate of hair growth also slows. Hair strands become smaller and have less pigment. So the thick, coarse hair of a young adult eventually becomes thin, fine, light-coloured hair. Many hair follicles stop producing new hairs.
Men tend to start showing signs of balding in their 20s to 30s, then most men are nearly bald by their 60s. However, some people can go bald earlier due to Male pattern baldness, Alopecia Areata, Stress, Illness and Medication.
Women also have similar causes of hair loss. Women loss their hair at a later stage of their life but there is still an increase as they get older. There are similar causes of hair loss in women including Female Pattern Baldness, Alopecia Areata, Stress, Pregnancy, Illness, Medication and Hormones.