Persons most commonly affected: Tends to occur most often in children and young adults. However, it can also affect older individuals.

Organ or part of body involved: Scalp

Symptoms and indications: In alopecia areata, the affected hair follicles are mistakenly attacked by a person‘s own immune system (white blood cells), resulting in the arrest of the hair growth stage. Alopecia areata usually starts with one or more small, round, smooth bald patches on the scalp and can progress to total scalp hair loss (alopecia totalis) or complete body hair loss (alopecia universalis). It is not contagious and is not caused by any food. It sometimes starts after a stressful event, but this is not usually the case. Alopecia areata has three stages. First there is sudden loss of hair, then enlargement of the patches of hair loss. Lastly new hair grows back. This may take months and sometimes years.

Causes and risk factors: Current evidence suggests that alopecia areata is caused by an abnormality in the immune system. This particular abnormality leads to autoimmunity. As a result, the immune system attacks particular tissues of the body. In alopecia areata, for unknown reasons, the body's own immune system attacks the hair follicles and disrupts normal hair formation. Biopsies of affected skin show immune cells inside of the hair follicles where they are not normally present. What causes this is unknown. Alopecia areata is sometimes associated with other autoimmune conditions such as allergic disorders, thyroid disease, vitiligo, lupus, rheumatoid arthritis, and ulcerative colitis. Sometimes, alopecia areata occurs within family members, suggesting a role of genes and heredity.