What Causes Hair Loss?

Don't worry too much about some hair in your shower drain. The Mayo Clinic estimates most people lose 50 to 100 hairs a day without any noticeable thinning. However, more serious hair thinning may be a cause for concern, and there may or may not be steps you can take to stop or reverse the damage. Hormones and genetics are the most common causes of hair thinning, but the thinning may also be a sign of a serious medical condition, stress or just hairstyles that abuse your hair.

Lifestyle Choices That Cause Hair Thinning

First, there are a couple of ways you may be unwittingly accelerating hair thinning. Traction alopecia is the technical term for hair thinning caused by overly tight braids and the overuse of some dyes, chemicals and irons, which can burn the scalp. An overview by two dermatologists on WebMD notes Sikh men and African-American women are among the most commonly affected groups.

Ironically, the hair extensions sometimes used to cover up hair thinning also may accelerate traction alopecia. Sometimes, the hair will grow back normally if there is no permanent scarring or root damage. However, in some cases, the damage from excessive hairstyling can be permanent, according to the WebMD dermatologists.

Hair thinning may also be a sign of poor nutrition or excessive stress. Dr. Andrew Weil, a famous integrative medicine expert, notes that inadequate iron or protein may cause hair thinning. Fad diets and crash diets are often ineffective in long-term weight loss, and can have dangerous side effects, such as hair thinning. Physical distress, such as a prolonged fever, or emotional distress, such as the death of a loved one, can cause temporary hair thinning. Watching hair suddenly thin may create further stress and worry, but the hair typically resumes its normal growth within a few months, according to the Mayo Clinic.

The clinic also notes that hair thinning is an occasional side effect of some birth-control pills, and drugs that treat gout, arthritis, depression and heart problems. Finally, a rare and mysterious mental illness, trichotillomania, causes people to compulsively pull out their hair, according to Mental Health America.

Genes and Hormones That Cause Hair Thinning

On the other hand, hormones and genetics are largely out of your control, but they are the most common type of hair thinning, and typically follow standard male patterns and standard female patterns. The National Institutes of Health describes the male pattern in an M shape from the top of the head and two sides of the forehead. In many men, the points will meet. The typical female pattern is quite different, with overall thinning, but no change in the hairline.

Each strand of hair grows from a follicle. These follicles can shrink over time, making the hair more short and fine. Eventually, the follicle is too small for any hair to grow. The NIH attributes this type of natural hair thinning to genetics and hormones, though the causes are not fully understood. Studies show that heredity can affect the age, rate and extent of hormonal hair thinning.

In other cases, temporary hormonal imbalances can lead to hair thinning, but the thinning can typically be reversed. Thyroid issues, pregnancy and childbirth can all cause hair thinning, which may not begin for three months after the hormonal change. It may also take another three months for normal hair growth to resume, according to the Mayo Clinic.

Disorders That Cause Hair Thinning

Mayo Clinic researchers also say other disorders, including diabetes and lupus, may also cause hair thinning. Scarring alopecia is caused by inflammation of the hair follicle. It coincides with other skin conditions, but it not well understood.

Another serious disorder, alopecia areata, is also not well understood, but the National Alopecia Areata Foundation offers information and help regarding the disease. It is an autoimmune disorder that typically strikes otherwise healthy people. Some research has found that a virus can trigger the disease in people who may have a family history of it. The hair will likely grow back, but the disorder might cause a lifelong cycle of rapid hair thinning and regrowth. Finally, ringworm or other infections can invade the hair and scalp, causing hair thinning.

Hormones often cause hair thinning, which is common and likely not medically dangerous. However, it may be a sign of a more serious condition, or a warning to change your lifestyle or hairstyle. Another cause of hair thinning can be dandruff, which can be helped with proper haircare and treatment.

Hair thinning can be attributed to disease, excessive hairstyling, malnutrition and stress. The good news is that hair thinning will sometimes stop and reverse itself.