Most hair loss is hormonal. Androgenetic alopecia — the receding hairline, the thinning crown — is driven by DHT acting on genetically susceptible follicles. The playbook is well established: block the hormone, support the follicle, wait.
Alopecia areata does not follow that playbook. It is caused by an immune system error. The body, for reasons that remain incompletely understood, begins to treat its own hair follicles as foreign tissue. The resulting hair loss is not a slow hormonal recession — it is rapid, patchy, sometimes total, and immunological in nature. Finasteride does nothing for it. Understanding what is actually happening is the prerequisite for treating it correctly.
What Alopecia Areata Actually Is
Hair follicles are unusual organs. Under normal conditions, they are protected from immune surveillance by what immunologists call "immune privilege" — the follicle actively suppresses local immune activity to prevent the kind of attack that would interrupt hair growth. This privilege is maintained by a local microenvironment that inhibits T-cell recognition and activity.
In alopecia areata, immune privilege collapses. Autoreactive CD8+ T-cells — immune cells that would normally be suppressed near the follicle — begin to recognise follicular antigens and mount an attack. The follicles are not destroyed; they are stunned into a premature, sustained resting phase. This is a critical distinction: the follicle remains viable beneath the scalp even when producing nothing visible.
The reversibility of alopecia areata — when it does reverse — is a consequence of this biology. Viable follicles that have been suppressed by immune activity can, under the right conditions, resume normal function.
What triggers the initial collapse of immune privilege is not fully established. Genetic susceptibility is significant: more than 25 genetic loci have been associated with alopecia areata, several of which overlap with other autoimmune conditions including type 1 diabetes, rheumatoid arthritis, and coeliac disease. Stress and acute illness are frequently cited as precipitating events by patients, and while the evidence for a direct causal link remains incomplete, the biological plausibility is real — cortisol and inflammatory signalling can disrupt the local follicular microenvironment.
Types and Patterns
Alopecia areata is not a single presentation. It exists across a spectrum of severity, and the pattern of hair loss has significant implications for prognosis and treatment choice.
Patchy alopecia areata is the most common form. One or more circular or oval patches of complete hair loss appear, most often on the scalp, though the beard, eyebrows, and eyelashes can all be affected. Individual patches are typically smooth and well-defined, with no scaling or scarring. The skin appears normal. In many cases — particularly the first episode in adults — spontaneous regrowth occurs within 12 months without any intervention.
Alopecia totalis describes complete loss of all scalp hair. This is a more severe presentation and is significantly less likely to resolve spontaneously than limited patchy disease. It requires active treatment rather than watchful waiting.
Alopecia universalis extends beyond the scalp to involve all body hair — eyebrows, eyelashes, axillary and pubic hair, and often body hair more broadly. This is the most severe form. Spontaneous complete remission in alopecia universalis is uncommon.
Ophiasis-pattern alopecia areata is a specific and prognostically important subtype characterised by band-like hair loss along the sides and lower back of the scalp — following the margins rather than presenting as central patches. The ophiasis pattern responds more poorly to standard treatments than patchy disease and carries a worse long-term outlook.
Sisaipho pattern (ophiasis in reverse) affects the central scalp while sparing the margins — the inverse of the typical ophiasis distribution. It is rarer and equally treatment-resistant.
Diagnosing Alopecia Areata
A confident clinical diagnosis is almost always possible without biopsy. The combination of clinical appearance, specific physical signs, and patient history is highly characteristic.
The pull test examines hairs at the active margin of a patch. In active alopecia areata, hairs at the periphery are easily extracted with minimal traction — a sign of ongoing disease activity. In stable or resolving disease, the pull test at the margin becomes negative.
Exclamation mark hairs are pathognomonic — a sign specific enough to confirm the diagnosis when present. These are short, broken hairs that taper toward their base, appearing widest at the tip and narrowest where they enter the scalp. They represent hairs that have been weakened at the follicle by immune attack.
Dermoscopy (trichoscopy) allows the examining clinician to see these signs clearly, along with black dots (cadaverised hairs), yellow dots (empty follicular ostia with sebaceous residue), and coiled hairs. Trichoscopy distinguishes alopecia areata from tinea capitis, trichotillomania, and scarring alopecias without requiring a biopsy.
Nail changes are present in approximately 10–20% of people with alopecia areata — the most common finding is pitting (small, regular depressions in the nail surface). Nail involvement does not change the treatment approach but can aid diagnosis in ambiguous presentations.
Blood tests are not required to diagnose alopecia areata, but they serve an important function: screening for concurrent autoimmune conditions that frequently co-occur. A baseline panel should include thyroid function (TSH, free T4), coeliac antibodies, and a full blood count. This is not a small precaution — thyroid autoimmunity is found in approximately 8–12% of people with alopecia areata, and unmanaged thyroid disease will impair hair regrowth regardless of the treatment used for the alopecia.
Treatment Options
Treatment for alopecia areata is stratified primarily by severity — the extent of scalp involvement, the duration of the current episode, and prognostic factors that influence how likely the disease is to respond or to persist.
Intralesional corticosteroid injections remain the first-line treatment for limited, patchy alopecia areata affecting less than 50% of the scalp. Triamcinolone acetonide is injected directly into affected areas at 4–6 week intervals. Response rates in patchy disease are reasonable — roughly 60–70% of patients show some regrowth. The limitation is practical: injections do not address the underlying immune drive, and relapse after stopping treatment is common. For extensive or rapidly progressing disease, intralesional injections are insufficient.
Topical and oral corticosteroids are used less commonly. Topical high-potency steroids have modest evidence for mild patchy disease. Short courses of systemic corticosteroids can temporarily suppress active disease and are sometimes used to arrest rapidly spreading involvement, but the disease typically rebounds on cessation and long-term systemic steroid use is not appropriate.
Topical immunotherapy (DPCP or SADBE) involves deliberately sensitising the scalp to a contact allergen, then applying progressively higher concentrations to induce a controlled local allergic reaction. The immune response provoked by the irritant appears to disrupt the autoimmune attack on follicles. This sounds counterintuitive and is mechanistically not fully understood — but response rates in extensive disease (50–80% scalp involvement) are substantial: approximately 40–60% of patients achieve significant regrowth. It requires monthly clinic visits and careful titration, and is typically only available in specialist hair loss clinics.
Minoxidil does not address the immune mechanism of alopecia areata. However, it is commonly used as an adjunct to immunosuppressive treatments — particularly during the recovery phase — to accelerate and support regrowth once immune suppression has allowed follicles to re-enter the growth phase. It should not be used in isolation as the primary treatment.
JAK inhibitors represent the most significant advance in alopecia areata treatment in decades. Janus kinase (JAK) inhibitors block the JAK-STAT signalling pathway, which is a key mediator of the inflammatory cascade that drives the immune attack on follicles. In June 2022, baricitinib (Olumiant) received FDA approval for severe alopecia areata — the first systemic drug approved specifically for the condition. Ritlecitinib (Litfulo) followed in 2023, with approval specifically for alopecia areata including adolescents aged 12 and above.
Clinical trial data for baricitinib in the BRAVE-AA trials showed that approximately 35–40% of patients with severe alopecia areata (80%+ scalp hair loss) achieved at least 80% scalp coverage at 36 weeks — a clinically meaningful outcome in a population with very limited prior options. Ritlecitinib trials produced broadly similar response rates. These are substantial results for a disease that previously had no approved systemic option.
JAK inhibitors are not without risk. Considerations include infection susceptibility, lipid changes, and post-marketing safety signals that apply broadly across the class. They require monitoring and are indicated for severe disease where the benefit-risk calculation is clearly favourable. For limited patchy disease, they are not the appropriate starting point.
Prognosis — What to Expect
The natural history of alopecia areata is highly variable, and this variability is genuinely difficult to communicate without either overstating hope or understating it.
For limited patchy disease — one or two small patches appearing for the first time in an adult — spontaneous full regrowth within 12 months is the most likely outcome. This is not a blanket reassurance: approximately 30% of people with an initial patchy episode will go on to develop more extensive disease. But for a first presentation in an adult without other poor prognostic features, the probability of natural recovery without systemic treatment is real and worth naming clearly.
Poor prognostic markers — features associated with a greater likelihood of extensive, treatment-resistant, or persistent disease:
- Ophiasis or sisaipho pattern
- Onset in childhood or adolescence
- Duration longer than 12 months without spontaneous recovery
- Total or near-total scalp involvement at any point
- Nail involvement (particularly severe nail dystrophy)
- Personal or family history of atopy (eczema, asthma, allergic rhinitis)
- Concurrent autoimmune conditions
The psychological dimension of alopecia areata deserves acknowledgement. Hair loss that is rapid, patchy, and unpredictable — appearing without obvious cause and resolving or worsening on its own timeline — is distressing in a way that slow, pattern-predictable androgenetic alopecia is not. The psychiatric comorbidity data in alopecia areata consistently shows elevated rates of anxiety and depression compared to control populations. This is not incidental to the condition; it is part of it, and should be treated with the same seriousness as the dermatological component.
Frequently Asked Questions
Is alopecia areata hereditary? There is a genetic predisposition — having a first-degree relative with alopecia areata approximately doubles your risk compared to the general population. But the condition is not deterministic in the way that androgenetic alopecia is. Many people with a strong family history never develop it. The genetic component appears to be one of susceptibility, requiring environmental or immunological triggers to manifest.
Can alopecia areata be permanently cured? No treatment currently alters the underlying autoimmune predisposition. JAK inhibitors and corticosteroids suppress disease activity while they are used; most patients who stop treatment experience relapse. The exception is spontaneous, durable remission — which does occur, particularly in limited patchy disease, but cannot be reliably induced by current treatments. This is the primary unmet need in alopecia areata research.
Is finasteride or minoxidil helpful for alopecia areata? Finasteride targets DHT — a hormone with no role in alopecia areata. It is not useful and is not indicated. Minoxidil addresses only the growth phase of the follicle and does not address immune suppression; it is used as an adjunct, not a primary treatment. Using finasteride for alopecia areata is a category error.
How is alopecia areata different from other forms of hair loss? The most important distinction is mechanism. Androgenetic alopecia is hormonal — DHT miniaturises follicles progressively. Telogen effluvium is event-triggered — a systemic shock pushes follicles into the resting phase simultaneously. Alopecia areata is immunological — T-cells suppress an otherwise healthy follicle. Each requires a completely different treatment approach. Applying the wrong treatment is not merely ineffective; it delays the correct diagnosis.