Sudden Round Bald Patch on the Scalp: What It Could Mean

What does alopecia areata look and feel like?

Alopecia areata classically appears as one or more round or oval patches of complete hair loss on the scalp. The skin inside the patch usually looks completely normal — smooth, the same color as surrounding skin, not scaly or scarred. It often appears suddenly; many people notice it when someone else points it out or they feel it while washing their hair.

The patches tend to be painless, though some people describe mild tingling or itching just before a patch forms. At the edges of an active patch, you may see short, tapered hairs that look like exclamation points ("exclamation-mark hairs") — a sign that loss is still spreading. This trichoscopic finding is among the most specific signs of active alopecia areata 1Ref 1Mubki T, Rudnicka L, Olszewska M, Shapiro J (2014).Evaluation and diagnosis of the hair loss patient: part II. Trichoscopic and laboratory evaluations.Trichoscopic findings in alopecia areata (yellow dots, black dots, exclamation-mark hairs) and differential diagnosis from tinea capitis and scarring alopecias. The condition can also affect eyebrows, eyelashes, and beard hair, not just the scalp 2Ref 2American Academy of Dermatology (2024).Hair Loss Resource Center.Clinical description of alopecia areata: autoimmune suppression of follicles, possibility of spontaneous regrowth, and the workup approach.

Why does alopecia areata happen, and who gets it?

Alopecia areata is an autoimmune condition — the body's immune system mistakenly targets hair follicles. The follicles are not destroyed, just suppressed, which is why hair can regrow. The exact trigger is not fully understood, but stress, illness, and genetic factors all appear to play a role 2Ref 2American Academy of Dermatology (2024).Hair Loss Resource Center.Clinical description of alopecia areata: autoimmune suppression of follicles, possibility of spontaneous regrowth, and the workup approach.

It can happen at any age, including in children, and affects people of all backgrounds. Having another autoimmune condition — such as thyroid disease or type 1 diabetes — modestly increases the likelihood. Alopecia areata affects approximately 2% of people over a lifetime and is not contagious. It is not caused by anything you did.

Most people with a single small patch have a good chance of spontaneous regrowth within a year, though recurrence is possible 2Ref 2American Academy of Dermatology (2024).Hair Loss Resource Center.Clinical description of alopecia areata: autoimmune suppression of follicles, possibility of spontaneous regrowth, and the workup approach.

What else could a round bald patch be?

While alopecia areata is the most likely explanation for a sudden smooth round patch, a clinician will consider other causes:

Tinea capitis (scalp ringworm) — a fungal infection that can cause patchy hair loss, typically with scaling, redness, or broken hair stubs. More common in children and in close-contact settings. This is important to distinguish from alopecia areata because tinea capitis requires oral antifungal treatment 1Ref 1Mubki T, Rudnicka L, Olszewska M, Shapiro J (2014).Evaluation and diagnosis of the hair loss patient: part II. Trichoscopic and laboratory evaluations.Trichoscopic findings in alopecia areata (yellow dots, black dots, exclamation-mark hairs) and differential diagnosis from tinea capitis and scarring alopecias.

Traction alopecia — from tight hairstyles. Creates loss along the hairline or where tension is greatest, not usually in a random round spot 3Ref 3Billero V, Miteva M (2018).Traction alopecia: the root of the problem.Traction alopecia as a differential diagnosis: location along hairline where hairstyle tension is applied, rather than random round spot.

Trichotillomania — a hair-pulling habit, sometimes unconscious. Creates irregular patches with broken hairs of different lengths.

Scarring alopecia — rarer, but would show signs of inflammation (redness, tenderness, scaling) and requires prompt treatment since follicle damage can become permanent.

How is alopecia areata evaluated by a clinician?

A dermatologist will examine the patch with dermoscopy (trichoscopy) — a handheld magnifying instrument that reveals specific microscopic patterns. In alopecia areata, trichoscopy characteristically shows yellow dots, black dots, broken hairs, and exclamation-mark hairs; this pattern helps distinguish it from tinea capitis and scarring alopecias without requiring a biopsy in most cases 1Ref 1Mubki T, Rudnicka L, Olszewska M, Shapiro J (2014).Evaluation and diagnosis of the hair loss patient: part II. Trichoscopic and laboratory evaluations.Trichoscopic findings in alopecia areata (yellow dots, black dots, exclamation-mark hairs) and differential diagnosis from tinea capitis and scarring alopecias.

Blood work for thyroid function and autoimmune markers is often ordered, since thyroid disease and other autoimmune conditions co-occur with alopecia areata more frequently than in the general population. A scalp biopsy may be recommended in diagnostically uncertain cases or when a scarring condition needs to be excluded.

What treatment options exist for alopecia areata?

Treatment options range from watchful waiting for small, stable patches to topical, injected, or oral medications that help calm the immune response and encourage regrowth. For mild cases, corticosteroid injections directly into the patch are a well-established first approach.

A major advance came in 2022 when the FDA approved baricitinib, an oral JAK1/JAK2 inhibitor, as the first systemic therapy specifically indicated for severe alopecia areata in adults. In phase 3 trials, approximately 38% of patients on the higher dose achieved significant scalp coverage at 36 weeks compared to around 5% on placebo 4Ref 4Freitas E, Guttman-Yassky E, Torres T (2023).Baricitinib for the Treatment of Alopecia Areata.FDA approval of baricitinib (2022) as first systemic therapy for severe alopecia areata; ~38% of patients achieved significant hair regrowth at 36 weeks vs ~5% on placebo. Two additional oral JAK inhibitors (ritlecitinib, deuruxolitinib) have since received approval for severe cases.

A specialist can advise whether systemic treatment is appropriate for your situation based on the extent and duration of hair loss.