A bald spot on your head is most commonly caused by alopecia areata, an autoimmune condition that affects about 2% of the global population. But several other conditions can also produce a distinct patch of hair loss, from fungal infections to tight hairstyles to compulsive hair pulling. The cause matters because some bald spots grow back on their own while others become permanent without treatment.
Alopecia Areata
Alopecia areata is the most well-known cause of sudden, circular bald patches. It happens when your immune system mistakenly attacks your own hair follicles. Specifically, a type of white blood cell called CD8+ T cells identifies hair follicle cells as threats and launches a direct assault. These T cells release inflammatory signals that damage the follicle and push the hair into its resting phase, causing it to fall out.
What makes alopecia areata persistent is a feedback loop. The attacking T cells produce a chemical signal that causes cells around the follicle to release another signal, which in turn activates even more T cells. This cycle amplifies the damage and can cause patches to expand or new ones to appear. Some of these immune cells also settle into the skin as long-lived “memory” cells, which helps explain why patches sometimes recur in the same spot.
The lifetime risk of developing alopecia areata is roughly 1.7% to 2.1%, and the peak incidence falls between ages 20 and 34. A typical patch is round or oval, smooth, and skin-colored, with no flaking or redness. You might notice it suddenly, sometimes after a period of stress, though many people have no identifiable trigger. The good news: follicles are not destroyed, just dormant. New hair often becomes visible three to six months after the immune attack subsides, with full density returning over the course of a year. For localized patches, steroid injections into the scalp produce a positive response in roughly 83% of patients.
Traction Alopecia
If your bald spot sits along your hairline, temples, or wherever your hair is pulled tightest, the cause may be traction alopecia. This is hair loss from sustained physical tension on the follicle. Hairstyles most commonly linked to it include cornrows, locs, tight braids, tightly pulled ponytails or buns, hair extensions or weaves (especially on chemically relaxed hair), and rollers worn to bed regularly. Even the constant rubbing of a hat, headscarf, or other head covering can contribute, particularly if you pull hair back tightly underneath it.
Early traction alopecia is reversible. You may notice small bumps around the follicles, tenderness, or broken hairs along the affected area. If you change your hairstyle and reduce tension, the hair generally grows back. But when the pulling continues long enough, the follicles scar over. At that point the skin looks smooth and shiny where hair used to grow, and regrowth is no longer possible. The American Academy of Dermatology emphasizes that the longer traction alopecia goes untreated, the more likely it becomes permanent.
Fungal Scalp Infections
Tinea capitis, a fungal infection of the scalp, can create bald patches that look quite different from alopecia areata. Instead of smooth skin, you’ll typically see scaling, flaking, or crusting within the patch. One hallmark pattern is called “black dot” tinea capitis: the fungus invades hair shafts and causes them to break right at the scalp surface, leaving behind tiny dark stubble that looks like black dots scattered across the patch.
Tinea capitis is most common in children and is contagious through shared combs, hats, or pillows. Swollen lymph nodes in the neck are a telltale sign that points toward a fungal cause rather than an autoimmune one. Unlike alopecia areata, fungal infections require antifungal treatment (usually taken by mouth, since topical creams can’t penetrate the hair shaft deeply enough). Once the infection clears, the hair regrows.
Trichotillomania
Trichotillomania is a condition where a person repeatedly pulls out their own hair, often without fully realizing they’re doing it. It creates bald patches that look distinctly different from other causes. The patches tend to have irregular, odd shapes rather than clean circles. The skin within the patch feels stubbly, and the remaining hairs are broken at varying lengths, sometimes with split or frayed ends. This uneven texture is a key visual clue that distinguishes pulled hair from hair that fell out on its own.
Trichotillomania is classified as a body-focused repetitive behavior, related to conditions like skin picking. People often pull during periods of stress, boredom, or intense concentration. Hair regrows when the pulling stops, but long-term pulling can eventually damage follicles enough to thin regrowth permanently.
Telogen Effluvium
Telogen effluvium is a diffuse shedding that doesn’t always create a single distinct bald spot, but it can thin certain areas enough to expose the scalp noticeably. It happens when a physical or emotional stressor pushes a large number of hair follicles into their resting (shedding) phase at the same time. Hair loss typically appears two to three months after the triggering event.
Common triggers include high fever, severe infections, childbirth, major surgery, significant psychological stress, thyroid disorders, stopping birth control pills, and crash diets low in protein. The delay between trigger and shedding is what confuses most people: by the time clumps of hair start falling out, the original stressor may be long over. If a doctor tugs gently on a section of your hair and multiple strands come loose easily, that positive “pull test” points toward active telogen effluvium. Acute episodes resolve within six months, and hair density returns to normal once the underlying cause is addressed.
Scarring Alopecia
Scarring alopecia is a group of conditions where inflammation destroys the hair follicle entirely and replaces it with scar tissue. The result is permanent hair loss. The affected skin looks smooth and shiny, similar to late-stage traction alopecia, but the key diagnostic feature is that the tiny openings in the skin where hairs normally emerge are completely closed over.
Several specific conditions fall under this umbrella. Central centrifugal cicatricial alopecia typically starts at the crown and spreads outward, most commonly affecting Black women. Lichen planopilaris causes patchy loss with redness and scaling around individual follicles. Frontal fibrosing alopecia creates a band-like recession of the hairline, often affecting the eyebrows and temples as well.
Because scarring alopecia destroys follicles, early treatment is critical. Once a biopsy shows scar tissue without active inflammatory cells, a stage called “end-stage scarring alopecia,” the damage is done and treatment becomes far less effective. Any bald spot that feels unusually smooth, shows no signs of tiny hairs trying to regrow, or is accompanied by burning, itching, or pain at the edges warrants prompt evaluation.
How Doctors Tell the Difference
Distinguishing between these causes starts with a careful look at the patch itself. Smooth, round patches without scaling suggest alopecia areata. Flaky, crusty patches with broken “black dot” hairs suggest a fungal infection. Irregular patches with hairs of different lengths point toward trichotillomania. Thinning along the hairline where tension is applied suggests traction alopecia. Smooth, shiny skin with no visible follicle openings raises concern for scarring alopecia.
Your history fills in the rest. A doctor will ask about recent stressors, hairstyling habits, new medications, and family history of autoimmune disease. A pull test, where several hairs are gently tugged, helps identify active shedding conditions. When the cause isn’t clear from appearance and history alone, a small scalp biopsy can reveal whether follicles are inflamed, scarred, or under immune attack, each of which points to a different diagnosis and a different path forward.