A sudden 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 distinct patches of hair loss, and the appearance of the spot itself offers strong clues about what’s going on. The shape, skin texture, and surrounding hair all help narrow down the cause.
Alopecia Areata: The Most Common Cause
Alopecia areata happens when your immune system mistakenly attacks hair follicles, causing hair to fall out in small, round patches roughly the size of a quarter. The bare skin underneath typically looks smooth and normal, with no rash, redness, or scarring. Around the edges of the patch, you may notice short broken hairs that are narrower at the base than at the tip, sometimes called “exclamation point” hairs. These are a hallmark sign.
Some people feel tingling, burning, or itching on the skin right before the hair falls out. The condition peaks between ages 20 and 34, though the 10-to-24 age range is considered a high-risk period overall. It’s slightly more common in women. The course is unpredictable: some people have a single episode and the hair grows back on its own, while others develop recurring patches throughout their lives. In children under 10, it tends to be more extensive and progressive. Sometimes hair regrows in one spot while new patches form elsewhere, and small patches can merge into larger ones.
Fungal Infection (Ringworm of the Scalp)
If your bald spot looks scaly, inflamed, or has tiny black dots, a fungal infection called tinea capitis is a strong possibility. The black dots are hair shafts that have broken off right at the scalp surface. The surrounding skin often looks silvery and flaky, and the patches tend to slowly expand over time. Your scalp may feel tender or painful in the affected area, and the remaining hair nearby is brittle and breaks easily when touched or pulled.
In more severe cases, a raised, spongy swelling called a kerion can develop. It drains pus and forms thick yellow crusting. This represents an intense inflammatory reaction to the fungus and needs treatment promptly to avoid permanent damage. Ringworm of the scalp is contagious and spreads through direct contact or shared items like combs and hats, so early identification matters.
Tight Hairstyles and Traction Alopecia
Hair loss from repeated pulling or tension follows a predictable pattern. It shows up where your hairstyle exerts the most force, and the hairline is usually the first place affected. Tight ponytails, braids, cornrows, buns, and extensions can all cause it. The warning signs include pain or stinging on the scalp, crusting, and a tenting effect where sections of skin get visibly pulled upward. A useful rule from the American Academy of Dermatology: if your hairstyle feels painful, it’s too tight.
Traction alopecia is reversible if you catch it early and switch to looser styles. But if the tension continues for months or years, the follicles can become permanently damaged, and the hair won’t return.
Hair-Pulling Disorder
Trichotillomania is a condition where a person repeatedly pulls out their own hair, sometimes consciously and sometimes without realizing it. The scalp is the most common site, though eyebrows and eyelashes are also affected. The resulting bald patches tend to have an irregular shape with hairs of varying lengths, since new growth keeps getting pulled at different stages. Some people pull specific types of hair or follow the same ritual each time. The location of patches can shift over time as pulling habits change.
Scarring vs. Non-Scarring Hair Loss
One of the most important distinctions is whether the bald spot involves scarring. In non-scarring hair loss (like alopecia areata), the hair follicles remain intact beneath the surface. The hair can potentially grow back because the follicle is still alive. In scarring alopecia, an inflammatory or autoimmune process destroys the follicle entirely, and the skin where hair used to be looks smooth and shiny. Some forms also cause redness, flaky skin, or blisters. Scarring alopecia causes permanent hair loss in the affected area.
Autoimmune conditions like lupus can cause scarring hair loss on the scalp. Discoid lupus lesions typically appear as reddish or violet-colored patches, often on the top of the head, with visible scarring, discoloration, and scale. The skin may show plugged or thickened follicle openings. These patches can be itchy, tender, or burning, though sometimes they cause no symptoms at all. If your bald spot has any discoloration, scarring texture, or visible inflammation, that points toward a scarring process that needs medical evaluation sooner rather than later.
Thyroid Problems and Diffuse Thinning
Thyroid disorders more commonly cause overall thinning rather than distinct bald spots. You’d notice decreased hair density across the entire scalp, excessive shedding during washing or brushing, and changes in hair texture (drier, coarser, more prone to breakage). Thinning can extend to eyebrows, eyelashes, and body hair. However, thyroid autoimmune conditions do increase your risk of developing alopecia areata, so a thyroid problem could indirectly lead to patchy hair loss. If you’re experiencing fatigue, weight changes, or temperature sensitivity alongside hair loss, a thyroid connection is worth investigating.
What a Dermatologist Will Check
A dermatologist can usually narrow down the cause through a few simple in-office tests. During a pull test, the doctor grasps about 40 strands and gently tugs. If six or more come out, that confirms active hair loss. A tug test checks whether strands break in the middle when held at both ends, which reveals brittleness or fragility. For a card test, the doctor parts your hair and holds a felt-covered card against the scalp to count and examine new or broken hairs that would otherwise be invisible.
These exams, combined with the visual appearance of the patch, are often enough for a diagnosis. In some cases, a scalp biopsy or blood work may be needed, particularly if lupus or another autoimmune condition is suspected.
Treatment Options
Treatment depends entirely on the cause. For alopecia areata, steroid injections into the patch are one of the most effective options. In clinical trials, about 83% of patients responded positively to these injections. They’re typically repeated every few weeks until regrowth is established. Topical treatments that stimulate blood flow to the follicle (like minoxidil) are sometimes used as well, though they work better for pattern hair loss than for autoimmune patches, and regrowth results for alopecia areata are modest.
Fungal infections require antifungal medication, usually taken by mouth since topical creams alone can’t penetrate the hair shaft. Traction alopecia improves when you eliminate the source of tension. For trichotillomania, behavioral therapy is the primary treatment. Scarring alopecia focuses on stopping the inflammatory process to preserve remaining hair, since destroyed follicles can’t regenerate.
For many people with a single small patch of alopecia areata, the hair grows back on its own within several months without any treatment. But patches that persist, expand, or show signs of scarring or infection benefit from earlier intervention.