Alopecia areata: the sudden bald patches explained
Last updated September 3, 2026.
Alopecia areata is an autoimmune condition that causes sudden, smooth, round bald patches, most often on the scalp, when the immune system attacks hair follicles. It can affect anyone, often starts in childhood or young adulthood, and its course is famously unpredictable: hair may regrow fully, patchily, or not at all, and episodes can recur.
What does it look like?
One or more completely smooth, round or oval bald patches, usually a few centimetres across, appearing over days to weeks. The scalp in the patch looks normal: no scaling, no scarring, no redness. A telltale sign is exclamation-mark hairs at the patch edge: short hairs that are narrower at the base. It can also affect the beard, eyebrows, and eyelashes. Some people notice nail changes (fine pitting). There is usually no pain or itch, though some feel tingling before hair falls.
Why does it happen?
The immune system mistakenly attacks the hair follicles, pushing them into a resting state; the follicles are stunned, not destroyed, which is why regrowth is possible. It runs in families and clusters with other autoimmune conditions, especially thyroid disease and vitiligo. Stressful events are often reported before onset, though the causal link is unclear. It is not caused by hair products, hats, or anything you did to your hair.
What actually helps?
- Watchful waiting: for one or two small patches, especially a first episode, up to half regrow within a year without treatment; a review every few months tracks progress.
- Steroid injections: corticosteroid injected into scalp patches is the most effective treatment for limited disease; regrowth usually begins within 4-8 weeks.
- Topical steroids and minoxidil: less effective than injections for patches, but useful for areas where injections are impractical and as maintenance.
- Extensive disease: for alopecia totalis (whole scalp) or universalis (all body hair), options include immunotherapy, oral steroids, and newer JAK inhibitor tablets approved for severe cases.
- Cosmetic and emotional support: wigs (NHS provision exists in the UK for qualifying cases), eyebrow and scalp camouflage, and alopecia support organizations all genuinely help.
When is it an emergency?
Hair loss itself is never an emergency, but not all hair loss is alopecia areata. See a doctor promptly if the scalp is red, scaly, scarred, or painful (suggesting other diagnoses), if hair loss comes with fatigue, weight change, or feeling cold (thyroid), or if a child develops patchy hair loss with scaling (possible ringworm, which is contagious and needs treatment). Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
What a Pymander AI doctor consult looks like
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Common questions
Will my hair grow back?
The honest answer: probably, at least partially, but nobody can promise. For a first episode with one or two patches, around half regrow within a year even without treatment, and steroid injections push the odds higher. The factors that lower the odds: onset in childhood, extensive disease, involvement of the scalp margin (ophiasis pattern), nail pitting, and other autoimmune conditions. Follicles are stunned rather than destroyed, so regrowth remains possible even years later, though it becomes less likely over time.
Is alopecia areata caused by stress?
Stress is the explanation everyone reaches for, and the evidence is genuinely mixed: many people report a stressful event in the months before onset, but controlled studies have not confirmed a causal link. The established driver is autoimmunity, often with a genetic predisposition. It is worth saying plainly: you did not cause this by being stressed, and reducing stress (while good for you) is not a treatment. Treat the autoimmunity, support your wellbeing, and let the evidence-based treatments do the work.
Is it contagious, and is it related to ringworm?
Alopecia areata is not contagious at all; it is autoimmune. Ringworm of the scalp (tinea capitis) is the condition it gets confused with, and ringworm is contagious, which is why the distinction matters. Ringworm patches are scaly, itchy, often inflamed, with broken hairs, while alopecia areata patches are completely smooth with normal-looking skin. Any scaly, inflamed patch of hair loss, especially in a child, needs assessment for ringworm because it requires antifungal treatment.
What are JAK inhibitors and can I have them?
JAK inhibitors (baricitinib, ritlecitinib, deuruxolitinib) are tablets that block the immune signal driving the attack on follicles, and trials show substantial regrowth in severe alopecia areata. They are approved for severe disease (typically alopecia totalis or extensive patchy loss) rather than a couple of small patches. They require ongoing use to maintain regrowth and carry the side-effect considerations of immune-modulating drugs, so the decision belongs with a dermatologist.
Will it spread to all my hair?
Most cases stay limited. A first episode of one or two patches progresses to total scalp loss (alopecia totalis) in a minority, and to total body hair loss (alopecia universalis) in a small percentage. Early limited disease has the best prognosis. Warning signs of a more aggressive course: rapid appearance of many patches, loss at the scalp margin, and childhood onset. If your loss is progressing fast, early dermatology referral matters because treatments work best before follicles have been dormant for long.
Can I get a wig on the NHS?
Yes, in the UK, wigs are available on the NHS for people with medical hair loss, including alopecia areata. You get a prescription from your consultant or GP, entitling you to acrylic wigs at the standard NHS charge (or free if you qualify for free prescriptions); human-hair wigs are available in some circumstances. Practical tips: many people prefer sourcing their own wig with a grant toward the cost, and support organizations like Alopecia UK maintain lists of wig suppliers and fitters who understand medical hair loss.