How is hair loss classified?

There are numerous ways to classify hair loss. One useful way has been to classify hair loss by whether the loss is localized (small area) and patchy or whether it affects large areas or the whole scalp (diffuse). Other medical classifications for hair loss include scarring versus non-scarring hair loss and are beyond the scope of this article.

What are causes of hair loss?

There are many causes of scalp hair loss, and they do differ in men and women. This article will cover the common ones. Studies show that losing up to 100-150 hairs per day is normal. Human hair naturally grows in three phases: anagen, catagen, and telogen. Anagen is the active or growing phase. Catagen is a fairly short phase of the natural hair cycle during which hairs begin to break down. Telogen is the resting phase. The hairs that are shed daily are often in the resting or late phase in the hair cycle. Normally, about 10% of the scalp hairs are in the resting or telogen phase at any time. These hairs are not growing and are getting prepared for cyclic shedding.