Human hair usually has a growth cycle.

It is made up of three periods: growth season; catagen season and telogen season.

The growth phase of hair is about three years, catagen phase is about three weeks and then there is a pause for about three months. This is continually repeated.

In contrast to animals that shed all their hair simultaneously at a certain time or season, humans’ hair has independent cycles.

For most people, 90 percent of hair belongs to the growth period and about 10 percent to telogen. Considering that 10 percent of telogen hair falls out in about three months when washing hair or at other times, the amount of daily hair fall is 0.1 percent of total hair.

Westerners have about 100,000 hairs, and 10 percent of them are telogen hairs, which means that 100 hairs could fall out a day. Koreans, however, have about 60,000-70,000 hairs. Generally, about 50-60 hairs could fall out daily, but alopecia could be diagnosed if more than 100 hairs fall out.

There are several reasons for alopecia. According to a report from the U.K., the amount of hair is minimized in spring, and then maximized in summer time, and then gradually reduced again since the seasons are linked to alopecia.

In other words, the amount of hair falling out in summer and autumn is relatively higher than in the spring and winter.

To prevent alopecia, it is always good to keep a clean scalp because an oily scalp can cause dandruff and inflammation, which can trigger alopecia.

As a body part, hair is influenced by body conditions. Thus unbalanced nutrition by dieting can cause alopecia as can physical or mental stresses.

Since it is natural for some hairs to fall out when washing, this is usually not the cause of alopecia. Therefore, it is important not to get stressed out through being too sensitive.

If the alopecia is progressing, a consultation with a dermatologist is advised. There are different types of alopecia so treatments should be used for the exact cause for a good result. 

By Lee Dong-youn

The author is an assistant professor at Department of Dermatologist of Samsung Medical Center. ― Ed.