[7] Psychological stress and illness are possible factors in bringing on alopecia areata in individuals at risk, but in most cases there is no obvious trigger.

[7][1] Alopecia areata is believed to be an autoimmune disease resulting from a breach in the immune privilege of the hair follicles.

[7] The underlying mechanism involves failure by the body to recognize its own cells, with subsequent immune-mediated destruction of the hair follicle.

[21] The hair tends to fall out over a short period of time, with the loss commonly occurring more on one side of the scalp than the other.

[22] Strong evidence of genetic association with increased risk for alopecia areata was found by studying families with two or more affected members.

[28][29] Lifestyle factors such as smoking, sleep quality, and obesity may also contribute to the onset and progression of alopecia areata.

[30] Studies indicate that smokers have a higher risk of developing the condition, potentially due to tobacco-induced Th17-mediated inflammation in hair follicles.

[33] Additionally, obesity is associated with an increased risk of alopecia areata, likely due to adipokine dysregulation, which promotes chronic low-grade inflammation and alters immune response, as seen in other inflammatory skin conditions.

[38] One possible explanation is that vaccinations could trigger immune system activation, which has been observed to exacerbate preexisting autoimmune or autoinflammatory conditions in at-risk populations.

[40] While causality remains unclear, these findings emphasize the need for further research into the relationship between vaccinations and AA progression.

Histologic findings may include peribulbar lymphocytic infiltration resembling a "swarm of bees", a shift in the anagen-to-telogen ratio towards telogen, and dilated follicular infundibulae.

[citation needed] Commonly, alopecia areata involves hair loss in one or more round spots on the scalp.

[11] A Cochrane-style systematic review published in 2019 showed 5% topical minoxidil was more than 8x more associated with >50% hair regrowth at 6 months compared to placebo.

[10] In cases of severe hair loss, limited success has been achieved by using the corticosteroid medications clobetasol or fluocinonide as an injection or cream.

Topical corticosteroids frequently fail to enter the skin deeply enough to affect the hair bulbs, which are the treatment target,[20] and small lesions typically also regrow spontaneously.

[50] For more severe cases, studies have shown promising results with the individual use of the immunosuppressant methotrexate or adjunct use with corticosteroids.

[51] When alopecia areata is associated with celiac disease, treatment with a gluten-free diet allows for complete and permanent regrowth of scalp and other body hair in many people, but in others, remissions and recurrences are seen.

[28] In June 2022, the U.S. Food and Drug Administration (FDA) authorized baricitinib, a Janus kinase (JAK) inhibitor, for the treatment of severe alopecia areata.

However, in an article published long-term follow-up; It is reported that the hair transplanted to the eyebrow area falls out again due to the recurrence of the disease.

This may not indicate a recurrence of the condition, but rather a natural cycle of growth-and-shedding from a relatively synchronised start; such a pattern will fade over time.

[20] Initial presentation most commonly occurs in the early childhood, late teenage years, or young adulthood, but can happen at any ages.

[22] Patients also tend to have a slightly higher incidence of conditions related to the immune system, such as asthma, allergies, atopic dermatitis, and hypothyroidism.

[59] People living in urban or economically disadvantaged areas face a higher likelihood of developing AA.

[59] The effects of the condition also differ by ethnicity: individuals of Black descent with AA are more likely to experience anxiety and require medical leave from work.

[59] These findings suggest that genetic, environmental, and social factors may influence both the likelihood of developing AA and its broader personal and professional impact.

[61] NASCAR driver Joey Logano, obstacle athlete Kevin Bull,[62] politicians Peter Dutton[63] and Ayanna Pressley,[64] K-pop singer Peniel Shin of BtoB,[65] actors Christopher Reeve,[66] Anthony Carrigan[67] and Alan Fletcher,[68] and actresses Jada Pinkett Smith,[69] May Calamawy,[70] and Lili Reinhart[71] all have some form of alopecia areata.