Hair Loss Information
Normal Hair Loss
The human scalp usually contains up to 150,000 hairs but anything down to 100,000 individual hairs would be considered normal. The hairs grow from sacks under the skin called follicles. The average follicle will produce hair at a growth rate of 1.75cm per month.
People lose hair on a daily basis as part of the normal growth and shedding cycle. This is completely natural and nothing to worry about. At any one time around 90% of the hairs are in the growing phase with the remainder being in the resting phase, which happens just before the hair falls out and is then replaced with another hair which will then be in its growth cycle for up to five years. Up to 150 hairs a day can be lost as part of this continuous process.
Male Pattern Baldness
The vast majority of cases of baldness in men are the result of something known as androgenic alopecia. As the name might suggest, this type of baldness is caused by a combination of hormonal and genetic factors. The typical pattern for hair loss of this nature is for hair to be lost at the crown and at the temples until the two areas meet in the middle causing a horseshoe shape of baldness to form. It is believed that around 25% of men start losing their hair by the age of 30.
Causes of Male Pattern Baldness
Many different hormones are responsible for regulating the hair on the human scalp but by far the most influential is testosterone and its extremely potent derivative - dihydrotestosterone (DHT.) DHT is responsible for shrinking the hair follicles in the scalp until they are incapable of supporting hair growth. Interestingly, the same DHT is responsible for the increase in the size of the hair follicles in other areas of the body such as the beard and underarm. Some men notice that as they lose hair on their head, they are growing it in other areas such as the back and the chest. The genetic differences between individual men may explain the different responses to DHT exposure with some men finding that their hair follicles are sensitive to the presence of androgens, manifested by the shrinkage and eventual death of the hair follicle and others who appear to be able to resist any threat to the viability of the hair follicles.
Other Types of Hair Loss
Alopecia Areata is a specific type of hair loss that involves the shedding of hair in small patches on the scalp or other parts of the body. This form of alopecia is thought to be caused when the immune system attacks the hair follicles. We do not know why the immune system attacks the hair follicles in this way but it could be triggered by stress.
Alopecia areata normally results in small clumps of hair falling out which may not re-grow for 12 months. Sometimes the hair does not grow back with the same pigmentation. It is not unusual for the hair to grow back white. In rare cases the alopecia affects the whole of the scalp. Approximately 10% of people who have this type of hair loss will not re-grow hair and this is usually the case where there is a family history of alopecia areata or the person has an autoimmune disorder.
Alopecia totalis is where the person loses all of the hair on his or her scalp. It is not clear what causes this but it is thought that it could be triggered by an autoimmune disorder or stress.
Alopecia universalis describes when a person is unable to grow any hair at all on their body or scalp. It can strike its victims at any age and is thought to be the result of an autoimmune disorder. This disorder appears to affect less than 1 person in 100,000.
Traction alopecia occurs when excessive strain is put on the hair shafts, usually through braiding. Prolonged traction of the hair can lead to permanent damage, with the hair refusing to re-grow.
Telogen effluvium describes a temporary thinning of the hair on the scalp. It is not known what causes telogen effluvium but it is probably caused by more hairs being in the shedding part of the cycle than the growing cycle. Telogen effluvium is therefore temporary as the hairs will normally re-grow.