Understanding Hair Loss: The Fundamentals

What Exactly Is Hair Loss?

Except for the palms of our hands and the soles of our feet, our eyelids, and belly buttons, hair grows everywhere on human skin, yet many hairs are so thin that they are nearly undetectable. Hair is composed of keratin, a protein generated in hair follicles in the skin’s outer layer. As follicles develop new hair cells, old cells are pushed out through the skin’s surface at a rate of around six inches every year.

The visible hair is a thread of dead keratin cells. The typical adult head contains 100,000 to 150,000 hairs and loses up to 100 of them every day; a few stray hairs on your brushes are not the reason for concern.

Approximately 90% of the hair on a person’s scalp is growing at any given moment. Each follicle has its life cycle, which is affected by age, sickness, and a range of other circumstances. There are three stages in this life cycle:

Anagen – active hair growth that typically lasts two to eight years.
Catagen – two to three weeks of transitional hair growth
Telogen – a resting period that lasts approximately two to three months; at the end of the resting phase, the hair is lost, replaced by a new hair, and the growth cycle begins again.

Hair growth diminishes as individuals become older. There are several forms of hair loss, generally known as alopecia:

What Factors Contribute to Hair Loss?

Medical problems. Hair loss can be caused by thyroid illness, lupus, diabetes, iron deficiency anemia, eating disorders, and anemia. Unless there is scarring, as in some instances of lupus, lichen planus, or follicular diseases, hair will usually regrow when the underlying problem is addressed.

Diet. Temporary hair loss can also be caused by a low-protein or extremely calorie-restricted diet. Learn about the foods that can help prevent hair loss.