Most people normally shed 50 to 100 hairs a day. But with about 100,000 hairs in the scalp, this amount of hair loss shouldn't cause noticeable thinning of the scalp hair. As people age, hair tends to gradually thin. Other causes of hair loss include hormonal factors, medical conditions and medications.
The most common cause of hair loss is a hereditary condition called male-pattern baldness or female-pattern baldness. In genetically susceptible people, certain sex hormones trigger a particular pattern of permanent hair loss. Most common in men, this type of hair thinning can begin as early as puberty.
Hormonal changes and imbalances can also cause temporary hair loss. This could be due to pregnancy, childbirth, discontinuation of birth control pills or the onset of menopause.
A variety of medical conditions can cause hair loss, including:
- Thyroid problems. The thyroid gland helps regulate hormone levels in your body. If the gland isn't working properly, hair loss may result.
- Alopecia areata. This disease occurs when the body's immune system attacks hair follicles — causing smooth, roundish patches of hair loss.
- Scalp infections. Infections, such as ringworm, can invade the hair and skin of your scalp, leading to hair loss. Once infections are treated, hair generally grows back.
- Other skin disorders. Diseases that can cause scarring, such as lichen planus and some types of lupus, can result in permanent hair loss where the scars occur.
Hair loss can be caused by drugs used to treat:
- Heart problems
- High blood pressure
Hair loss can also result from:
- A physical or emotional shock. Many people experience a general thinning of hair several months after a physical or emotional shock. Examples include sudden or excessive weight loss, a high fever, or a death in the family.
- Hair-pulling disorder. This mental illness causes people to have an irresistible urge to pull out their hair, whether it's from the scalp, their eyebrows or other areas of the body. Hair pulling from the scalp often leaves patchy bald spots on the head.
- Certain hairstyles. Traction hair loss can occur if the hair is pulled too tightly into hairstyles