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.
In general, most hair loss is not associated with systemic or internal disease, nor is poor diet a frequent factor. Frequently, hair may simply thin as a result of predetermined genetic factors, family history, and the overall aging process. Many men and women may notice a mild and often normal physiologic thinning of hair starting in their thirties and forties. Other times, normal life variations including temporary severe stress, nutritional changes, and hormonal changes like those in pregnancy, puberty, and menopause may cause a reversible hair loss.
Notably, several health conditions, including thyroid disease and iron deficiency anemia, can cause hair loss. While thyroid blood tests and other lab tests, including a complete blood count (CBC), on people who have ordinary hair loss are usually normal, it is important to exclude underlying causes in sudden or severe hair loss. If you are concerned about some other underlying health issues, you may start by seeing your family physician, internist, or gynecologist for basic health screening. Dermatologists are doctors who specialize in problems of skin, hair, and nails and may provide more advanced diagnosis and treatment of hair thinning and loss. Sometimes a scalp biopsy may be taken to help in diagnosis of severe or unexplained hair loss.
Although many medications list “hair loss” among their potential side effects, drugs are also not overall common causes of thinning or lost hair. On the other hand, with cancer treatments and immune suppression medications including chemotherapy, hair loss is a very common side effect. Complete hair loss often occurs after a course of major chemotherapy for cancer. Usually, hair regrows after six to 12 months.
Women lose hair on an inherited (genetic) basis, too, but the female pattern tends to be more diffuse, with less likelihood of the crown and frontal hairline being lost. Although some women may notice hair thinning as early as their 20s, the pace of hair loss tends to be gradual, often taking years to become obvious to others. There seems to be a normal physiologic thinning that comes with age and occurs in many women in their early to mid 30s. More women have underlying causes of hair loss than men. These include treatable conditions like anemia and thyroid disease. In particular, women with a form of thyroid disease called Hashimoto’s autoimmune thyroiditis may have hair loss. These conditions are diagnosed by blood tests. Although a few studies have suggested that baldness may be inherited through the mother’s family genes, these theories require further testing. Current studies are inconclusive.
While stories about hats choking off follicles or long hair pulling on the roots may be more folklore, repeat hair trauma like tightly woven hair pulled back and consistent friction can potentially worsen or cause localized hair loss in some individuals. Black individuals who pull their hair tightly back in a rubber band can develop a localized hair loss at the front of the scalp.
Hair loss “myths” of special concern to women:
Longer hair does not necessarily put a strain on roots.
Shampooing does not accelerate hair loss; it just removes those that were ready to fall out anyway.
Coloring, perming, and conditioning the hair do not usually cause hair loss. Burns or severe processing may cause hair loss and breakage. Styles that pull tight may cause some loss, but hair coloring and “chemicals” usually don’t.