A small, round bald spot that appears suddenly on your head is most often caused by alopecia areata, an autoimmune condition that affects roughly 0.2% of the global population. But it’s not the only possibility. Fungal infections, tight hairstyles, stress-related shedding, and even unconscious hair pulling can all produce a noticeable bare patch. The cause matters because it determines whether the hair will grow back on its own, needs treatment, or requires a change in habits.
Alopecia Areata: The Most Common Cause
If you woke up one day and noticed a smooth, coin-sized bald spot with no redness, flaking, or scarring, alopecia areata is the leading suspect. It happens when your immune system mistakenly attacks the cells at the base of hair follicles, essentially telling healthy hair to stop growing and fall out. The immune cells cluster around follicles in what pathologists describe as a “swarm of bees” pattern, shutting down hair production in a localized area.
The patches are typically round or oval with sharp borders, and the surrounding hair looks completely normal. Some people notice “exclamation point” hairs at the edges of the spot: short, broken strands that are narrower at the base than the tip. The spot itself usually feels smooth rather than rough or scaly. You might have one patch or a few, and they can appear anywhere on the scalp.
The good news is that hair follicles are not destroyed in alopecia areata. They’re dormant, not dead, which means regrowth is possible. Many people see hair return within several months without any treatment. For patches that persist, steroid injections into the scalp every four to six weeks are the standard approach. Studies show that 62% to 87% of people treated this way achieve more than 75% regrowth within 12 to 24 weeks. The catch: about one in four people experience the patch returning after successful treatment.
Fungal Infection (Ringworm of the Scalp)
A bald spot that comes with itching, redness, or flaking may not be autoimmune at all. Tinea capitis, a fungal infection commonly called scalp ringworm, causes patches of hair loss that look distinctly different from alopecia areata. The skin inside the patch is often scaly or irritated, especially around the edges, and can resemble severe dandruff concentrated in one area.
One hallmark is “black dot” tinea capitis, where the fungus infects hair shafts and causes them to break off right at the scalp surface, leaving dark stubble dots across the bare patch. More severe cases can develop into a kerion, a swollen, pus-filled area that’s painful to touch. Kerions can cause permanent scarring if left untreated, so a patch that’s oozing or tender warrants prompt attention. Tinea capitis is contagious and more common in children, though adults can get it too, particularly through shared combs, hats, or pillows.
Tight Hairstyles and Physical Damage
If your bald spot sits along your hairline, temples, or the edges of your scalp, the cause may be mechanical. Traction alopecia develops from prolonged or repeated tension on hair follicles. Braids, cornrows, tight ponytails, weaves, extensions, and dreadlocks are the most common culprits. The risk goes up significantly when tension is applied to hair that’s already been chemically relaxed or heat-straightened, because those treatments weaken the hair shaft and make it more prone to breakage.
Ballet dancers, military personnel, and anyone whose daily routine involves pulling hair tightly away from the face are at higher risk. Early traction alopecia is reversible. If you change the hairstyle before the follicles are permanently damaged, the hair typically grows back. But years of repeated tension can destroy follicles entirely, replacing them with scar tissue and making the loss permanent. The key signal is where the loss appears: traction alopecia follows the line of tension, usually the frontal hairline or the area around the ears.
Hair Pulling (Trichotillomania)
Some people pull their own hair without fully realizing it, especially during periods of stress, boredom, or concentration. Trichotillomania is a behavioral condition where the urge to pull becomes repetitive and difficult to resist. The scalp is the most common site, followed by eyebrows and eyelashes.
The resulting bald patches tend to look different from alopecia areata. They’re often irregularly shaped rather than neatly round, and the patch contains broken hairs of varying lengths rather than being uniformly smooth. Many people develop rituals around the pulling: combing through hair with their fingers, feeling individual strands, or selecting hairs based on texture or length. Some distribute their pulling across a wide area to make the thinning less obvious, which can delay recognition of the pattern.
Stress-Related Shedding
A major physical or emotional stressor, such as surgery, high fever, significant weight loss, childbirth, or severe psychological distress, can push a large number of hair follicles into their resting phase all at once. This condition, called telogen effluvium, produces noticeable shedding two to four months after the triggering event. That delay is what makes it confusing: by the time your hair starts falling out, the original stressor may be long over.
Telogen effluvium usually causes diffuse thinning rather than a single isolated patch, but the shedding can be uneven enough to create areas that look noticeably thinner. Once the trigger is removed, shedding typically stops within three to six months. Visible regrowth follows, though it can take 12 to 18 months before hair density looks cosmetically normal again.
Scalp Inflammation and Skin Conditions
Chronic scalp conditions like psoriasis and seborrheic dermatitis can cause temporary hair loss in affected areas. Scalp psoriasis produces thick, dry, silvery scales that often extend beyond the hairline onto the forehead or behind the ears. Seborrheic dermatitis looks similar but tends to be oilier, with yellowish, greasy flakes. Both cause itching, and repeated scratching can worsen hair loss in the inflamed zone. The hair usually returns once the underlying inflammation is controlled.
Nutritional Deficiencies
Low iron levels are one of the more underrecognized contributors to hair loss. Ferritin, the protein that stores iron in your body, is the standard screening marker. Many dermatologists consider supplementation when ferritin drops below 70 ng/mL, even if standard blood work says your iron is technically “normal.” Iron deficiency doesn’t always produce a single bald spot the way alopecia areata does, but it can cause enough thinning in one area to create a visible gap, especially if combined with other factors.
How to Tell if Hair Will Grow Back
The critical distinction is whether the follicles themselves are intact or destroyed. In non-scarring conditions like alopecia areata, telogen effluvium, and early traction alopecia, the follicles are preserved beneath the surface and retain the ability to produce hair again. You might notice fine, light-colored “peach fuzz” regrowing in the bare area, which is a reassuring sign.
In scarring alopecia, the follicles are permanently replaced by fibrous tissue. The skin in the bald area may look shiny, smooth, or slightly discolored, and you won’t see any tiny hairs emerging. The oil glands that normally sit alongside hair follicles are also destroyed, so the skin can feel unusually dry compared to the surrounding scalp. Scarring alopecia accounts for a smaller percentage of cases, but catching it early is important because treatment focuses on stopping the scarring from spreading rather than regrowing what’s already lost.
If your bald spot is smooth with no redness or scaling, appeared suddenly, and is roughly the size of a coin, alopecia areata is the most likely explanation, and the odds of regrowth are strongly in your favor. If the spot is itchy, scaly, tender, or slowly expanding, a different cause is more likely, and identifying it sooner gives you more options.