# Alopecia areata medical overview > Live situation record from CLSTR: https://clstr.news/situations/alopecia-areata-medical-overview > Updated: 2026-09-29T13:49:26.000Z. Sources: 20. Developments: 2. Alopecia areata is an unpredictable autoimmune condition affecting approximately 2% of the global population. According to dermatologist Enilde Borges Costa of the Brazilian Society of Dermatology (SBD), the disease occurs when the body attacks hair follicles, preventing healthy hair growth. The condition manifests in three primary forms: localized patches on the scalp, total alopecia (complete loss of scalp hair), and universal alopecia (total loss of all body hair, including eyebrows and eyelashes). Episodes are often cyclical, alternating between hair loss and regrowth. Diagnosis is performed through clinical physical examination, as there are currently no definitive laboratory or imaging tests to identify the condition. While the disease has a genetic component and can be triggered by factors such as infections, it is not classified as a purely psychological illness. Beyond physical symptoms, the condition can have significant psychological impacts, and some patients have reported complications from conventional treatments, such as osteopenia resulting from long-term corticosteroid use. ## Timeline ### 2026-09-29: Alopecia areata causes unpredictable hair loss in 2% of population Alopecia areata is an autoimmune disease causing unpredictable hair loss. It can affect the scalp or the entire body and is diagnosed through clinical examination rather than laboratory tests. 2 sources. https://clstr.news/cluster/alopecia-areata-causes-unpredictable-hair-loss-in-2-of-population ### 2026-09-27: Alopecia areata: Understanding the autoimmune hair loss condition Alopecia areata is an unpredictable autoimmune disease affecting 2% of the world. It causes cyclical hair loss and carries significant emotional and physical challenges for patients. 18 sources. https://clstr.news/cluster/alopecia-areata-causes-unpredictable-hair-loss --- Cite as: Alopecia areata medical overview. CLSTR, https://clstr.news/situations/alopecia-areata-medical-overview