We have hair all over our bodies. Hair grows from the root, which is under the skin and is the only part of the hair that is alive. The rest of the hair is made up of dead protein cells.
Hair Growth Speed
Hair growth rate is genetically determined, and varies from person to person. It also grows more slowly with age, and is affected by both internal states and environmental conditions.
Hair Growth in the Summer
Hormones released in the body during the summer season can increase the rate of growth. However, the increase in growth rate is so small that it is likely to go unnoticed.
Other Changes in the Summer
Researchers report that while hair grows, hair shedding also increases in spring and summer. By fall, a person may lose as many as 100 hairs per day. This shedding may also affect hair growth, and varies from person to person.
Research suggests that hair shedding is related to daylight, and that reducing exposure to sunlight may help prevent seasonal hair shedding.
Hair Growth Cycles
It sometimes seems as if your hair is growing fast. Just two weeks after a haircut, you may notice the need for a trim. Then, suddenly, the growth seems to slow down or stop; you go many weeks in a row during which your hair seems to stay exactly the same length. What's happening here?
Not only does hair grow faster in the summer, but it goes through cycles of growth and rest all year long. Each complete cycle typically lasts several weeks.
More About Hair Growth Cycles
There are three stages of hair growth: anagen, which is the active growth phase; catagen, a transitional stage; and telogen, a resting phase. Three percent of hair is in the catagen stage at any time. During the anagen growth phase, hair typically grows about one centimeter per month.
The active growth phase is called anagen. The transitional stage is called catagen. The resting phase is called telogen.