More than half of men and women in the United States experience hair loss. About 30% of people have hair loss by age 30 years, and about 50% have hair loss by age 50 years. Hair loss is so common that most of the time it is considered a normal variation and not a disease. Other animals closely related to humans, such as the chimpanzee, also lose their hair.
Forms of hair loss
Androgenic alopecia - The most common type of hair loss, also called male pattern baldness
Traumatic alopecia - Hair loss from hair being torn out
Drug-induced alopecia - Hair loss caused by one of many medications
Alopecia areata - Patchy, usually reversible, hair loss
Hair loss varies widely with race.
Japanese men develop baldness less commonly than whites do. On average they also develop balding about 10 years later.
Blacks are 4 times less likely to have abnormal hair loss than are whites.
Women develop hair loss as frequently as men do, but because of hormonal differences women don’t lose as much hair volume.
Differences in hair styling allow women to hide hair loss more effectively than men.
A woman may not notice hair loss itself but may notice that her ponytail or braid is getting thinner.
Women also have a different pattern of balding than men.
Hair loss has few medical complications, but several serious conditions can cause it. In addition, there are some psychological effects associated with going bald. People with hair loss may sometimes be more likely to have a negative body image than those without hair loss.
There are 3 cycles of hair growth–growing, resting, and shedding.
In most animals these cycles change with the season, and all hairs are in the same part of the cycle at the same time. This is why animals grow a thicker coat in the fall and shed most in the spring.
Unlike most animals, in humans each hair has its own pattern of growing, resting, and shedding.
Each person sheds hair and regrows hair every day.
When this balance is disturbed and more hairs are shed than are regrown, alopecia or hair loss results.