Bald spots on the scalp almost always signal one of a handful of identifiable conditions, and the cause matters because it determines whether the hair will grow back on its own, needs treatment, or requires urgent attention to prevent permanent loss. Some causes are autoimmune, some mechanical, some infectious, and some related to stress or hormones. Below are eight of the most common reasons bald patches appear, along with the clues that help distinguish them and what you can do about each one.
1. Alopecia Areata
Alopecia areata is the condition most people picture when they think of sudden, round bald spots. It is autoimmune: your immune system mistakenly attacks hair follicles, causing smooth, coin-shaped patches of hair loss that can appear seemingly overnight. The disease affects roughly 5.3 million people in the United States alone, making it one of the most common autoimmune conditions.1PubMed Central. Genetic basis of alopecia areata: a roadmap for translational research The patches are usually completely bare or contain a few short, tapered “exclamation mark” hairs near the edges.
Hair follicles normally enjoy a degree of protection from the immune system, a status researchers call immune privilege. In alopecia areata, that protection breaks down, and immune cells flood the base of the follicle, shutting down hair production.2PubMed. Hair follicle immune privilege and its collapse in alopecia areata Stress appears to be one trigger for this collapse, with research pointing to a stress-driven chain of events that exposes follicle proteins to the immune system and kicks off an inflammatory loop.3International Journal of Dermatology and Venereology. Immune Regulation in Hair Follicle Protection and Hair Regeneration: Insights from the Collapse of Immune Privilege in Alopecia Areata and Targeted Immunotherapy For many people, the spots fill in within a year without treatment, but the condition can recur or, in rarer cases, progress to total scalp or body hair loss.
2. Androgenetic Alopecia
Pattern hair loss is the most common form of hair loss overall, and while it typically thins gradually rather than creating sudden bare patches, it can produce noticeable bald spots at the crown or along the part line. In men, it tends to start at the temples and vertex; in women, it usually shows up as widening along the center part. A scoping review of 65 studies found that family history of pattern hair loss, smoking, poor diet, and higher body mass index were consistently reported risk factors, with many studies defining “early onset” as beginning before age 30.4PubMed Central. Factors associated with early-onset androgenetic alopecia: A scoping review
The underlying process involves hormonal sensitivity in certain follicles. Over time, affected follicles shrink and produce thinner, shorter hairs until some stop producing visible hair altogether. Because the thinning is gradual and patterned, it can be mistaken for normal aging when it actually responds well to treatment if caught early. Minoxidil and finasteride remain the first-line options for most people, though the scalp microbiome may also play a role: research has linked altered microbial populations and local inflammation to the follicular shrinkage seen in pattern baldness.5The Microbe. Unlocking the secrets of the hair microbiome: From scalp health to therapeutic advances
3. Telogen Effluvium
If you notice diffuse thinning or bald spots appearing roughly two to three months after a major illness, surgery, crash diet, childbirth, or period of intense emotional stress, telogen effluvium is the likely culprit. The mechanism is straightforward: a shock to the body pushes a large number of hair follicles out of their active growth phase and into a resting state prematurely. About two to three months later, those resting hairs fall out together.6PubMed. Telogen effluvium
Psychological stress alone can trigger telogen effluvium. Research shows that elevated cortisol and inflammatory signaling molecules disrupt normal hair-cycle timing, delay follicles from re-entering the growth phase, and contribute to the widespread shedding pattern.7JAAD Reviews. The role of psychological stress in hair loss: A review The good news is that telogen effluvium is almost always temporary. Once the trigger resolves, hair generally regrows within six to twelve months without specific treatment. The bad news is that the shedding can be alarming, with hundreds of hairs coming out daily during the worst of it.
4. Traction Alopecia
Traction alopecia is caused by repeated physical pulling on the hair. Tight ponytails, braids, cornrows, dreadlocks, weaves, and hair extensions are the usual offenders. It affects roughly a third of women of African descent who wear high-tension hairstyles for prolonged periods, and the risk climbs with the duration and tightness of the style, as well as the use of chemical relaxers.8PubMed Central. Traction alopecia: the root of the problem The condition also occurs in children and in anyone of any background who subjects their hair to sustained tension.9PubMed. Review of traction alopecia in the pediatric patient: Diagnosis, prevention, and management
The telltale sign is hair loss concentrated along the hairline, temples, or wherever the pull is strongest. Early on, you might notice small bumps or tenderness around the affected follicles. At this stage the damage is reversible if you switch to a looser style. If the pulling continues for years, however, follicles can scar over and the loss becomes permanent. The fix is prevention: rotating hairstyles, reducing tension, and avoiding chemical processes that weaken the hair shaft.
5. Tinea Capitis
Tinea capitis is a fungal infection of the scalp, most common in children but possible at any age. It typically produces one or several round bald patches that look different from alopecia areata because the skin inside the patches is often scaly, inflamed, or studded with tiny black dots where hairs have broken off at the surface. A dermatologist can often distinguish tinea from alopecia areata using a handheld magnifying device: fungal infections tend to show comma-shaped and corkscrew hairs along with visible scaling, while alopecia areata shows yellow dots and exclamation-mark hairs without significant scaling.10PubMed Central. Different Trichoscopic Features of Tinea Capitis and Alopecia Areata in Pediatric Patients Perifollicular scaling was present in nearly 90% of tinea cases in one study, reinforcing scaling as a key distinguishing feature.11PubMed Central. Trichoscopic and Clinico-Morphological Evaluation of Tinea Capitis
Tinea capitis requires oral antifungal medication; topical creams alone do not penetrate deeply enough to clear a scalp infection. With proper treatment, hair regrows fully in the vast majority of cases, though treatment courses often run six to eight weeks. The infection is contagious, spreading through shared combs, hats, and pillows, so treating close contacts and cleaning shared items matters.
6. Trichotillomania
Trichotillomania is a compulsive hair-pulling disorder classified alongside obsessive-compulsive conditions. People with trichotillomania repeatedly pull out their own hair from any body region, though the scalp is the most common site. The resulting bald patches tend to look irregular and oddly shaped, with hairs of different lengths scattered throughout, because the pulling is uneven and ongoing.12PubMed Central. Trichotillomania: What Do We Know So Far?
The condition affects women more often and is frequently denied or hidden, which can delay diagnosis. Unlike most other causes on this list, the scalp skin inside the patches usually looks normal because no infection, inflammation, or autoimmune attack is involved. A clue for clinicians is the “negative pull test,” meaning the remaining hairs are firmly rooted and don’t come out easily when gently tugged, which is the opposite of what you’d see in telogen effluvium or active alopecia areata. Treatment typically involves cognitive behavioral therapy, sometimes combined with medication for anxiety or compulsive behavior. The hair grows back normally once the pulling stops, provided the follicles haven’t been damaged by years of repeated trauma.
7. Scarring Alopecia
Scarring alopecias are a group of conditions in which inflammation destroys hair follicles and replaces them with scar tissue. The most recognizable of these is lichen planopilaris, which commonly appears as patches of hair loss at the top or sides of the scalp, often accompanied by itching, burning, or tenderness.13PubMed. A Practical Approach to the Diagnosis and Management of Classic Lichen Planopilaris Because the follicles are permanently destroyed, hair does not regrow in the scarred areas. That makes early diagnosis critical: the goal shifts from regrowing hair to stopping the inflammation before it spreads further.
Another form, folliculitis decalvans, is driven by bacterial infection and inflammation. It produces patches of scarring alopecia where multiple hair shafts emerge from a single dilated opening, creating distinctive tufts.14PubMed. Tufted folliculitis of the scalp: a distinctive clinicohistological variant of folliculitis decalvans The affected skin often looks shiny, smooth, and slightly pale compared to surrounding skin, and a scalp biopsy is frequently needed to confirm the specific type and guide treatment. If your bald spots show signs of scarring, redness at the edges, or pain, getting a dermatology evaluation quickly is important.
8. Chemical and Contact Reactions
Hair dye, bleach, chemical relaxers, and other harsh salon products can cause localized hair loss when they damage the scalp. In severe cases, chemical burns can create actual ulcers that heal with scarring, permanently destroying the follicles underneath. One documented case involved a teenager who developed a large scalp ulcer after a routine hair-dyeing session at a salon; the wound took eleven months to heal and left a permanent scar.15PubMed Central. Chemical Scalp Burn after Hair Coloring-Case Report with Literature Review
Even without a dramatic burn, allergic contact dermatitis of the scalp can cause hair thinning and loss. Scalp allergies are frequently misdiagnosed as dandruff because the symptoms overlap, including itching, redness, and flaking. But repeated exposure to the allergen worsens the inflammation around follicles and can lead to noticeable hair loss over time.16PubMed Central. Allergic contact dermatitis of the scalp: a review of an underdiagnosed entity A study tracking patients after episodes of scalp contact dermatitis found that half developed increased hair shedding two to four months later, consistent with a telogen effluvium triggered by the inflammatory insult.17JAMA Dermatology. Telogen Effluvium After Allergic Contact Dermatitis of the Scalp If your bald spots appeared after switching hair products or visiting a salon, an allergy evaluation and product change may be all that’s needed.
Less Common Causes Worth Knowing
A few rarer conditions can also produce bald patches and are easy to miss if you’re only thinking about the usual suspects. Secondary syphilis occasionally causes hair loss in a scattered, “moth-eaten” pattern, affecting somewhere between 3% and 7% of people in that stage of the infection.18PubMed Central. Alopecia syphilitica, from diagnosis to treatment The patches are non-scarring and resolve with antibiotic treatment, but because syphilis rates have been climbing in many countries, it’s a diagnosis worth considering when bald spots appear alongside other symptoms like rash or fatigue.
Radiation therapy to the head can also produce rectangular or irregularly shaped bald patches that correspond precisely to the radiation field, reflecting direct damage to actively growing follicle cells.19PubMed Central. Three Cases of Radiation-induced Temporary Alopecia with Hair Microscopic Examination Low-dose radiation usually causes temporary loss that recovers over months, while high-dose exposure can produce permanent damage. Chemotherapy more commonly causes diffuse shedding, but targeted brain radiation reliably produces localized bald patches.
How Nutritional Deficiencies Fit In
You’ll find countless articles listing iron and vitamin D deficiency as standalone causes of bald spots. The picture is actually more mixed than the internet suggests. Studies consistently find that people complaining of hair loss tend to have lower iron (ferritin) and vitamin D levels than healthy controls.20PubMed Central. Serum ferritin and vitamin D levels should be evaluated in patients with diffuse hair loss prior to treatment21PubMed. Serum ferritin and vitamin d in female hair loss: do they play a role? But having lower levels doesn’t prove they caused the shedding. A comprehensive analysis of multiple nutrients in telogen effluvium patients concluded that nutritional deficiencies were not as common as widely assumed and that other causes should be investigated before attributing hair loss to diet alone.22PubMed Central. A comprehensive investigation of biochemical status in patients with telogen effluvium
The practical takeaway: checking ferritin and vitamin D is reasonable when you’re losing hair, and supplementing a genuine deficiency won’t hurt. But don’t assume a supplement will fix the problem, and don’t let a normal blood result stop you from investigating other causes on this list.
How Doctors Tell These Apart
Many of these conditions can look similar to an untrained eye, and misdiagnosis is common. A few features help narrow things down before you even see a specialist. Smooth, completely bare patches with no scaling point toward alopecia areata. Scaly, inflamed patches in a child suggest tinea capitis. Hair loss concentrated along the hairline or wherever tension is applied points to traction alopecia. Irregular patches with hairs of varying lengths and normal-looking skin underneath suggest trichotillomania. And bald spots with shiny, pale, or scarred skin at the center signal scarring alopecia, which needs urgent evaluation.
When the clinical picture is ambiguous, a scalp biopsy can settle the question. Pathologists look at the type and pattern of inflammation, whether follicles have been replaced by scar tissue, and the ratio of actively growing to resting hairs. This information, combined with what the bald spots look like and how they’ve progressed, is usually enough to reach a diagnosis.10PubMed Central. Different Trichoscopic Features of Tinea Capitis and Alopecia Areata in Pediatric Patients If your patches aren’t responding to the treatment you’ve been given, or if you’ve been told it’s “just stress” but the patches keep spreading, push for a dermatology referral.
Treatment Developments for Alopecia Areata
Because alopecia areata is so common and so distressing, it’s worth highlighting how its treatment landscape has changed. JAK inhibitors, a class of drugs that dial down the overactive immune signaling behind the disease, have shown strong results. A pooled analysis of about 290 cases found that roughly 72% of patients responded, with nearly half achieving good regrowth and the average time to complete regrowth sitting around seven months.23PubMed. JAK inhibitors for alopecia areata: a systematic review and meta-analysis A separate trial of tofacitinib reported that about a third of treated patients achieved at least 50% improvement, though the effect depended on the subtype: patchy alopecia areata responded better than total scalp or body hair loss.24PubMed Central. Safety and efficacy of the JAK inhibitor tofacitinib citrate in patients with alopecia areata
The catch is that stopping the medication leads to relapse, on average within about eight and a half weeks in the tofacitinib trial.24PubMed Central. Safety and efficacy of the JAK inhibitor tofacitinib citrate in patients with alopecia areata That means these drugs work more like ongoing management than a cure. Still, for people with extensive or stubborn patches, JAK inhibitors represent the first real targeted therapy for the condition, and newer versions with better safety profiles continue to enter trials.25PubMed Central. Janus kinase inhibitors for alopecia areata: a review of clinical data
Platelet-rich plasma (PRP) injections have also attracted attention. In a placebo-controlled trial, patients receiving PRP showed measurable increases in hair density, averaging about 46 additional hairs per square centimeter compared to their baseline, along with microscopic evidence of thicker skin and more active follicles.26PubMed Central. The Effect of Platelet-Rich Plasma in Hair Regrowth: A Randomized Placebo-Controlled Trial PRP is not FDA-approved specifically for hair loss, and the evidence base is still relatively thin, but it offers a lower-risk alternative for people who aren’t candidates for systemic medication.
The Emotional Weight of Bald Spots
Hair loss hits harder psychologically than many people expect, and doctors historically haven’t taken it very seriously. A large study of nearly 600 alopecia areata patients found that more than 80% reported anxiety or depressive symptoms, and roughly two-thirds scored above the clinical threshold for anxiety on a validated screening tool.27British Journal of Dermatology. Psychosocial burden and the impact of illness perceptions and stigma on quality of life, anxiety and depression in alopecia areata: results from the Alopecia + Me study More than two-thirds reported feeling embarrassed by their condition often or always. Interestingly, people with moderate hair loss (covering 20% to 50% of the scalp) reported worse quality of life than those who had lost nearly all their scalp hair, possibly because partial loss feels more conspicuous and harder to conceal than total loss, where many people adopt headscarves or embrace the look.28PubMed Central. The Invisible Impact of a Visible Disease: Psychosocial Impact of Alopecia Areata
If your bald spots are affecting your mood, daily activities, or social life, that’s not an overreaction. It’s a well-documented consequence of the condition, and it’s a valid reason to pursue treatment even when the patches are medically “benign.” Connecting with a support group or a therapist experienced in appearance-related distress can help, particularly during the uncertain waiting periods that come with conditions like alopecia areata, where you don’t know whether the patches will spread or spontaneously resolve.
The Scalp Microbiome Connection
Emerging research suggests the microbial community living on your scalp and even in your gut may influence hair loss in ways that weren’t appreciated a decade ago. Disruptions in scalp microbial balance have been linked to several forms of alopecia, and certain bacteria and fungi can either promote or suppress local inflammation depending on how abundant they are and which strains dominate.5The Microbe. Unlocking the secrets of the hair microbiome: From scalp health to therapeutic advances A review of available evidence concluded that microbial imbalance on the scalp, within individual hair follicles, and in the gut all appear to play a role in the development of various forms of hair loss.29PubMed Central. The Gut and Skin Microbiome in Alopecia: Associations and Interventions
This is still early science, and nobody should be buying probiotic shampoos expecting miracles. But it may help explain why some people develop hair loss conditions and others don’t, even when their genetics, hormone levels, and stress exposure look similar. It also opens the door to future treatments that target the scalp ecosystem rather than just the immune system or hormones.