In humans, hair is an important indicator of individual characteristics such as self-image, identity, ethnicity and health, among other attributes. Hence, it is not surprising that diseases that result in hair loss lead to disorders related to self-esteem and psychosocial interactions. Therefore, in scalp conditions such as the various types of alopecias, prompt diagnosis and timely therapeutic intervention are of extreme importance in the prognosis of patients.
Normally, hair goes through a regular growth cycle. During the anagen phase, which lasts three to four years, the hair grows. During the telogen phase, which lasts about three months, the hair rests.
At the end of the telogen phase, the hair falls out and is replaced by new hair. The average person loses about 100 hairs each day. Hair loss also can have other causes, including drugs or disease.
As they age, men tend to lose the hair on top of their head, which eventually leaves a horseshoe-shaped ring of hair around the sides. This type of hair loss is called male-pattern baldness. It's caused by genes (from both parents - the idea that men take after their mother's father is a myth) and it's fueled by the male hormone, testosterone. In female-pattern baldness, the hair loss is different - it thins throughout the top of the scalp, leaving the hair in front intact.
A number of disorders can cause the hair to fall out. People who have an autoimmune condition called alopecia areata lose hair on their scalp, as well as on other parts of their body. Other health conditions that can cause excess hair loss include: