alopecia areata

alopecia areata, autoimmune disease characterized primarily by hair loss on the face and scalp and often also on other parts of the body. Alopecia areata usually is chronic and ranges from mild to severe, with some individuals experiencing only one episode of hair loss and others having episodes throughout their lives. Full hair regrowth occurs in some persons, but others experience only partial or no regrowth. Although there is no cure, treatments that can stimulate hair regrowth are available.

Types

There are several types of alopecia areata. Patchy alopecia areata, which is the most common form, is characterized by small round patches of hair loss, usually on the scalp. Alopecia totalis affects the scalp and is characterized by complete or almost complete hair loss. Alopecia universalis, which is rare, involves total or near total hair loss over the entire body. Two other types are diffuse alopecia areata, in which hair thins across the scalp, and ophiasis alopecia, in which hair loss occurs in a band along the sides and back of the head.

Epidemiology and risk factors

Globally, alopecia areata affects about 2 percent of individuals at some point in their lives. Anyone may be affected at any age. When the condition develops prior to age 10, hair loss tends to be more extensive and progressive. Persons who are Asian, Black, or Hispanic are more likely than white people to develop alopecia areata.

While the precise cause of alopecia areata is unclear, the condition is associated with multiple genetic variants. About 20 percent of persons who develop alopecia areata have an affected relative; risk is increased particularly if the relative is an immediate family member and if that individual was affected before age 30. Persons who have Down syndrome or polyglandular autoimmune syndrome type 1 are also more likely to develop the disease, as are those affected by other autoimmune conditions, such as celiac disease, certain diseases of the thyroid gland, lupus erythematosus, psoriasis, rheumatoid arthritis, type 1 diabetes mellitus, and vitiligo. Persons who have allergic or atopic conditions, including asthma, allergic rhinitis, or atopic dermatitis, are also at increased risk for alopecia areata. In addition, environmental factors, such as bacterial or viral infection, certain medications, or physical or emotional stress, may trigger an episode in predisposed persons.

Symptoms and complications

Alopecia areata frequently has a sudden onset. Some persons experience an itching, tingling, or burning sensation prior to initial hair loss, though the condition generally is painless. Hair loss can begin anywhere on the body. On the scalp, hair typically falls out in round or oval patches, and short, broken hairs that are wider at the tip than the base—sometimes referred to as exclamation points—are often found around the edges of a patch or within a patch. Facial hair loss can affect the beard area, the eyebrows, the eyelashes, and the nostrils. Usually, there is no rash or scarring on bare patches of skin. Persons who experience more extensive hair loss may also develop brittle nails, sometimes marked by pits, or tiny dents.

In about 50 percent of cases, hair regrowth takes place within one year of loss, without medical interventions. Hair regrowth is more likely for individuals with mild cases. Regrown hair is often initially white or gray, with later restoration of the person’s natural hair color. Less commonly, hair loss continues, and eventually the person experiences total hair loss over the entire body. Alopecia areata is associated with an increased risk of retinal disease, including retinal detachment, retinal vascular occlusion, and retinopathy. Owing to the significant role that hair can have in physical appearance, some individuals affected by alopecia areata secondarily develop anxiety or depression.

Diagnosis and treatment

Alopecia areata is diagnosed by visual examination, by biopsy of hair and sometimes also affected areas of skin, and, in some instances, by blood tests. Although there is no cure, there are treatment options for hair regrowth since hair follicles remain intact. Examples of treatments include injected corticosteroids, which help prevent the immune system from attacking hair follicles, and oral or topical minoxidil, which increases blood flow to the follicles and thereby facilitates hair growth.

Are you a student?

Get a special academic rate on Britannica Premium.

Subscribe

Patients with more severe hair loss may choose topical immunotherapy or Janus kinase (JAK) inhibitors, which block the JAK signaling pathway that leads to inflammation. In some cases, individuals with alopecia areata forgo medical treatment and instead favor the use of hairpieces or wigs, strategic hairstyles, scalp micropigmentation, or various head coverings, such as hats. Makeup, tattoos, microblading, or nano brows can cover hair loss in the eyebrows. Some persons also use false eyelashes, which can be attached with magnets or glue.