Hair loss

Hair loss, called alopecia or baldness, is the loss of hair from the scalp or body, usually involving at least the head. It can range from a small patch to complete body hair loss, and typically does not involve inflammation or scarring. For some people, it leads to psychological distress. The main types are male- or female-pattern hair loss, alopecia areata, and a temporary thinning called telogen effluvium. Male-pattern hair loss results from genetics combined with male hormones; female-pattern hair loss has an unclear cause; alopecia areata is an autoimmune condition; and telogen effluvium often follows a physically or psychologically stressful event, such as pregnancy.

Less common causes of hair loss without inflammation or scarring include pulling out hair, certain medications like chemotherapy, HIV/AIDS, hypothyroidism, and malnutrition from deficiencies in vitamin B12 or iron. Causes that do involve scarring or inflammation include fungal infections, lupus erythematosus, radiation therapy, and sarcoidosis. Diagnosis is partly based on which areas are affected. For pattern hair loss, treatment may simply mean accepting the condition, which can include shaving the head. Options like minoxidil, finasteride, or hair transplant surgery can be tried. Alopecia areata can be treated with steroid injections into the affected area, but these need frequent repetition. Hair loss is common: by age 50, about half of men and a quarter of women experience pattern hair loss, and about 2% of people develop alopecia areata at some point.

Baldness is the partial or complete lack of hair growth, part of the broader topic of hair thinning. Its degree and pattern vary, but the most common cause is androgenic hair loss, also called alopecia androgenetica or alopecia seborrheica, the last term used mainly in Europe. Hypotrichosis is a condition of abnormal hair patterns, mostly loss or reduction, often involving vellus hair growing where terminal hair should be. Hair growth is normal after birth, but soon the hair sheds and is replaced by sparse, abnormal hair that is fine, short, brittle, and may lack pigment. Baldness may appear by age 25.

Symptoms of hair loss include patches of hair loss, often circular, along with dandruff, skin lesions, and scarring. Alopecia areata typically shows in unusual areas like the eyebrows, back of the head, or above the ears, where male-pattern baldness usually does not occur. In male-pattern hair loss, thinning starts at the temples and crown, with hair thinning or falling out. Female-pattern hair loss occurs at the frontal and parietal areas. People have between 100,000 and 150,000 scalp hairs, and normally lose about 100 per day. To maintain volume, hair must be replaced at the same rate. Early signs include more hair in the brush or basin after shampooing, or a wider parting or thinning crown. A substantially blemished face, back, and limbs may point to cystic acne, the most severe form of acne, which arises from the same hormonal imbalances that cause hair loss and is linked to dihydrotestosterone production.

The psychology of hair thinning is complex. Hair is seen as essential to identity, especially for women, who often associate it with femininity and attractiveness, while men link a full head of hair with youth and vigor. People experiencing thinning may find their appearance conflicts with their self-image and worry they look older or less attractive. Psychological problems, if present, are usually worst at the onset. Two meta-analyses on androgenetic alopecia found average psychosocial distress levels to be moderate, not severe, and that balding men were no more likely to have depression or low self-esteem than non-balding men. Hair loss from chemotherapy can change self-concept and body image, and for most patients, body image does not return to its previous state even after hair regrows. Such patients may have trouble expressing feelings (alexithymia) and may avoid family conflicts; family therapy can help.

Causes of hair loss, though not fully understood, are many. Pattern hair loss in men is due to genetics and dihydrotestosterone; in women, the cause is unclear. Infections include dissecting cellulitis of the scalp, fungal infections like tinea capitis, folliculitis from various causes, Demodex folliculitis (caused by a mite that feeds on sebum and can cause thinning, especially on oily scalps), and secondary syphilis. Temporary or permanent hair loss can be caused by medications for blood pressure, diabetes, heart disease, and cholesterol.