Alopecia Areata (Patchy Hair Loss): Causes, Symptoms and Dermatologist Treatment
Alopecia areata is sudden hair loss in round or oval patches. The immune system mistakes the hair follicles for foreign tissue and attacks them, so hair falls out in patches while the scalp still looks normal: not red, no sores, no itching. It is not contagious and is not caused by improper hair care. The hair follicles are usually not permanently destroyed, so hair can grow back.
In this article, a dermatologist gives a quick overview of what causes alopecia areata, how it differs from other types of hair loss, which tests are done, and what evidence-based treatments are available today, including the newer JAK inhibitor medicines.
Quick Facts: Alopecia Areata
What it is: an autoimmune condition in which the immune system attacks the hair follicles, causing patchy hair loss.
Typical signs: hair loss patches with smooth edges and a normal scalp, no itching and no sores. "Exclamation mark hairs" may be seen at the edge of a patch.
Location: most often the scalp, but it can also affect the eyebrows, beard, eyelashes or body hair.
Associated signs: small pits in the nails (nail pitting) may occur, and the condition is linked with thyroid disease, vitiligo and allergies.
Outlook: many single patches regrow on their own within 6-12 months, but some cases become long-lasting or come back.
ICD-10: L63
Key point: the hair follicles are not permanently destroyed. Treatment can help hair regrow sooner.
What causes alopecia areata?
Alopecia areata is an autoimmune disease in which the immune system attacks hair follicles in the growth phase, so the hair stops growing and falls out. The follicles remain, which is why hair can regrow. Related factors include:
Genetics and immunity: it is often seen in people with a family history of autoimmune disease.
Common associated conditions: thyroid disease, vitiligo, atopic dermatitis and allergies.
Triggers: severe stress, illness or infection may trigger a flare in people who are predisposed.
A common misconception is that it is caused by washing hair the wrong way, using poor shampoo or poor nutrition. These are not causes of this condition.
What does alopecia areata look like?
Round or oval hair loss patches with smooth, clear edges that appear within a few weeks.
The scalp in the patch looks normal: not red, not flaky, no scales and no scarring.
Exclamation mark hairs (short, wider at the tip and narrow at the root) at the edge of a patch are a characteristic sign.
Nail changes such as tiny pits or roughness of the nail surface can occur together with it.
Several severity patterns: a single patch, multiple patches, loss along the edge of the scalp (ophiasis), loss across the whole scalp (alopecia totalis) or across the whole body (alopecia universalis).
How to tell alopecia areata from other types of hair loss
"Hair loss" has many types that are treated differently. Telling them apart correctly is the key to effective treatment:
Hereditary hair thinning (androgenetic alopecia): hair thins gradually over the top of the scalp or along the frontal hairline, without sharply defined patches, and progresses slowly.
Hair loss from the resting phase (telogen effluvium): diffuse shedding across the whole scalp, often after stress, childbirth, illness or weight loss, without sharply defined patches.
Fungal infection of the scalp (tinea capitis): patchy hair loss together with scaling, redness, itching or pustules and short broken hairs. It is common in children and needs oral antifungal medicine (unlike alopecia areata, where the scalp is normal).
Hair pulling (trichotillomania): irregularly shaped patches with hairs of mixed lengths from pulling.
Scarring hair loss (scarring alopecia): the scalp is red, sore or shiny, or follicle openings disappear. The lost hair usually does not regrow, unlike alopecia areata.
Rule of thumb: a hair loss patch with smooth edges and a normal scalp, without itching or scaling fits alopecia areata. If there is scaling, redness, itching or scarring, see a doctor, because it may be a different condition that needs different treatment.
Which tests are needed if alopecia areata is suspected?
Physical examination and scalp dermoscopy to look for exclamation mark hairs, black dots and other characteristic features.
Hair pull test to assess whether the condition is active.
Blood tests for associated conditions such as thyroid function, in people with an indication.
Biopsy is done only when the diagnosis is unclear or scarring hair loss is suspected.
Evidence-based treatment for alopecia areata
Treatment depends on severity, age and response. The aim is to calm the immune attack locally and stimulate hair regrowth. Evidence-based options include:
Corticosteroid injections into the patches (intralesional corticosteroid) are the main treatment for a limited number of patches in adults and work well.
Topical corticosteroids or other topical medicines such as medium- to high-potency steroids, suitable for children or people who cannot have injections.
Topical minoxidil is used as an add-on to stimulate hair regrowth.
Topical immunotherapy (such as DPCP/SADBE) for widespread, long-lasting cases, performed by a specialist doctor.
JAK inhibitor medicines such as baricitinib and ritlecitinib are newer medicines approved for severe alopecia areata and help hair regrow in many people. They must be used under a doctor's supervision with monitoring for side effects.
Severe cases (totalis/universalis) usually respond less well. The doctor will plan treatment individually.
Most single patches have a chance of regrowing on their own. Treatment speeds this up and improves the chance of regrowth, but no method can completely prevent recurrence.
When to see a dermatologist
Patches that spread quickly, multiple patches, or loss across the whole scalp or body
Scaling, redness, itching, pustules or scarring on the scalp (it may be a fungal infection or scarring hair loss)
Eyebrow, eyelash or beard hair loss at the same time
Obvious nail changes or symptoms of thyroid or other autoimmune disease
Emotional distress or loss of confidence: see a doctor to plan treatment and emotional support
Common myths about alopecia areata
"It is caused by washing hair too often or using bad shampoo." Not true. It is an autoimmune condition unrelated to hair washing.
"Alopecia areata means permanent baldness." Not always true. The hair follicles are usually not permanently destroyed and hair can regrow.
"It is contagious." It does not spread through touch or sharing belongings.
"You must take lots of supplements or vitamins to recover." The main treatment calms the immune attack locally, not taking vitamins indiscriminately.
"Ordinary hair growth products can treat it." Alopecia areata differs from hereditary hair thinning and must be treated by targeting the immune mechanism.
Frequently asked questions about alopecia areata
What is alopecia areata?
It is a condition in which the immune system attacks the hair follicles, causing sudden hair loss in round or oval patches while the scalp still looks normal: not red, not itchy, no sores. The follicles are usually not permanently destroyed.
What causes alopecia areata?
It is caused by the immune system attacking the hair follicles and is linked with genetics and other autoimmune conditions such as thyroid disease, vitiligo and allergies. Stress or illness may be a trigger. It is not caused by hair washing or poor nutrition.
Can alopecia areata go away on its own?
Many single patches have a chance of regrowing on their own within 6-12 months, but some cases become long-lasting or come back. Treatment speeds up regrowth and improves the chance of recovery.
How is alopecia areata different from hereditary hair thinning?
Alopecia areata causes sharply defined patches that appear quickly because of the immune system, whereas hereditary hair thinning gradually thins the top of the scalp or the frontal hairline. The treatments are therefore completely different.
How is alopecia areata treated?
For a limited number of patches, doctors often use corticosteroid injections into the patches or topical steroids, together with minoxidil. More extensive cases may use topical immunotherapy or JAK inhibitor medicines such as baricitinib and ritlecitinib under a doctor's supervision.
Is alopecia areata contagious?
No. It is an individual's own immune condition and does not spread through touch or sharing combs, hats or belongings.
If you have sharply defined hair loss patches that appeared quickly, or hair loss that is spreading, see a dermatologist for diagnosis and early treatment planning. Consult a dermatologist at Siam Dermatology, phone +66 61 448 7000 or LINE @siamderm.
Written by Dr. Patara Voravutinon, Dermatologist · Last reviewed August 22, 2026
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