Bald spots on the scalp usually point to one of a handful of causes, and the most common by far is alopecia areata, an autoimmune condition where your immune system mistakenly attacks hair follicles. But infections, tight hairstyles, nutritional gaps, and even unconscious habits can also leave noticeable patches. The pattern of the bald spot, what the skin looks like underneath, and whether you have other symptoms all help narrow down what’s going on.
Alopecia Areata: The Most Common Cause
Alopecia areata causes sudden, round or oval patches of hair loss on the scalp. The immune system targets hair follicles and triggers inflammation that stops growth. The bare patches typically look smooth, with no rash, redness, or scarring on the exposed skin. One telltale sign: short broken hairs around the edges of the patch that are narrower at the base than the tip, sometimes called “exclamation point” hairs.
Patches can appear on other parts of the body too, including the beard area, eyebrows, and eyelashes. Some people develop a single patch that regrows on its own within months. Others develop multiple patches or experience recurring episodes over years. The condition can start at any age, though it often first appears in childhood or early adulthood.
The good news is that the hair follicles are not destroyed. They’re essentially dormant, which means regrowth is possible. Steroid injections into the affected area are one of the most studied treatments. A meta-analysis in the Journal of the American Academy of Dermatology found that these injections produced meaningful hair regrowth in roughly 77% to 81% of patients, depending on the concentration used, with treatments typically given every three to four weeks over a course of six weeks to six months.
Scalp Infections That Cause Patches
A fungal infection called tinea capitis (scalp ringworm) can create bald patches that look very different from alopecia areata. Instead of smooth bare skin, you’ll typically see scaling, flaking, or a raised ring-shaped rash. The affected area often appears red on lighter skin and gray or brown on darker skin. In more severe cases, the skin can become swollen, crusty, or ooze fluid if a bacterial infection develops on top of the fungal one.
Scalp ringworm is contagious and more common in children, though adults can get it too. It spreads through direct contact or by sharing combs, hats, or pillows. Unlike alopecia areata, it requires antifungal treatment to resolve, and hair typically grows back fully once the infection clears.
Tight Hairstyles and Traction Alopecia
If your bald spots line up with areas where your hair is pulled tightest, the cause may be traction alopecia. This happens when repeated tension on the hair follicles damages them over time. The hairline is one of the first places affected, and early signs include broken hairs around your forehead, a gradually receding hairline, and small patches where the pull is strongest.
Hairstyles that commonly cause this include tight cornrows, locs, braids, high ponytails, buns, and hair extensions or weaves, especially on chemically relaxed hair. Even wearing rollers to bed regularly or constantly rubbing a tightly secured headscarf can contribute. Caught early, traction alopecia is reversible once you switch to looser styles. Left too long, the follicle damage becomes permanent.
Hair Pulling You Might Not Notice
Trichotillomania is a condition where a person repeatedly pulls out their own hair, sometimes without realizing it. It often targets the scalp, eyebrows, or eyelashes and leaves patchy bald spots with hairs of uneven lengths. Some people pull automatically while reading, watching TV, or resting their head on a hand. Others do it deliberately to relieve tension or anxiety, sometimes following specific rituals like searching for a particular type of hair.
A hallmark of the condition is an increasing sense of tension before pulling, followed by a feeling of pleasure or relief afterward. Most pulling happens in private, and many people try repeatedly to stop without success. If this sounds familiar, it’s worth knowing that trichotillomania is a recognized medical condition with effective behavioral treatments, not a personal failing.
Scarring Alopecia: When Patches Feel Different
Most causes of bald spots leave the follicle intact, meaning hair can eventually regrow. Scarring alopecia is the exception. Conditions like lichen planopilaris cause inflammation that permanently destroys hair follicles and replaces them with scar tissue. If your bald patches come with scalp pain, itching, burning, or red and scaly skin, scarring alopecia is a possibility.
Lichen planopilaris is the leading cause of scarring hair loss. Symptoms can come on quickly or develop gradually. Early treatment is critical because once a follicle is scarred over, that hair will not return. The goal shifts from regrowth to preventing further loss.
Stress, Illness, and Delayed Shedding
A condition called telogen effluvium can cause noticeable hair loss two to three months after a major stressor. Surgery, high fever, significant weight loss, childbirth, or severe emotional stress can all push a large number of hair follicles into their resting phase at once. When those hairs eventually fall out weeks later, the timing gap makes it hard to connect cause and effect.
Telogen effluvium typically causes diffuse thinning across the whole scalp rather than distinct bald spots. But if you’re noticing thinning patches and recently went through a physically or emotionally stressful period about three months ago, this may be the explanation. Acute episodes usually resolve on their own within six months once the trigger has passed.
Low Iron and Thyroid Problems
Nutritional deficiencies, particularly low iron stores, are linked to hair shedding. Women with hair loss in one study had average ferritin (stored iron) levels of about 16 ng/mL compared to 60 ng/mL in women without hair loss. You don’t need to be clinically anemic for low iron to affect your hair. If your diet is low in red meat, leafy greens, or legumes, or if you have heavy periods, iron may be worth checking.
Thyroid disorders, both overactive and underactive, can also trigger hair loss. This usually shows up as diffuse thinning rather than distinct patches. However, having a thyroid autoimmune condition like Hashimoto’s increases your risk of developing alopecia areata, which does cause patchy loss. If you’re experiencing bald spots alongside fatigue, weight changes, or temperature sensitivity, a thyroid check is reasonable.
How Doctors Figure Out the Cause
A dermatologist can often identify the cause of bald spots just by examining your scalp. One simple in-office test involves grasping about 40 strands of hair and gently tugging. If six or more strands come out, that indicates active hair loss and helps guide the next steps.
If the appearance of the patches isn’t clear-cut, or if the skin on the bald spot looks unusual, a small scalp biopsy may be needed. This is particularly useful for distinguishing between different types of scarring alopecia, where treatment decisions depend on knowing the exact cause. Blood work to check iron levels, thyroid function, and inflammatory markers can also help rule out systemic causes.
The appearance of the bald spot itself gives important clues. Smooth, bare skin with no irritation suggests alopecia areata. Redness, scaling, or itching points toward infection or scarring conditions. Broken hairs along the hairline suggest traction. Uneven hair lengths in the patch raise the possibility of pulling. Paying attention to these details before your appointment helps your dermatologist reach a diagnosis faster.