Medical conditions

A variety of medical conditions can cause hair loss:

• Alopecia areata.This type of nonscarring hair loss is called patchy hair loss. It occurs when the body’s immune system attacks hair follicles — causing sudden hair loss that leaves smooth, roundish bald patches on the skin. It is an autoimmune disorder.
• Scalp infections.Fungal infections, such as ringworm, can invade the hair and skin of your scalp, leading to scaly patches and hair loss. Once infections are treated successfully with an antifungal agent hair generally grows back.
• Other skin disorders.Diseases that cause scarring alopecia may result in permanent loss at the scarred areas. These conditions include lichen planus, some types of lupus and sarcoidosis.
• Hair-pulling disorder.This condition, also called trichotillomania, causes people to have an irresistible urge to pull out their hair, whether it’s from the scalp, the eyebrows or other areas of the body.