Scalp fungus is a fungal infection of the scalp and hair shafts caused by a group of fungi called dermatophytes. The medical name is tinea capitis, and it’s essentially ringworm of the scalp. It produces round, scaly patches where hair breaks off, and it requires oral antifungal medication to clear because the fungus lives inside the hair shaft itself, where topical creams and shampoos can’t reach.
What Causes It
Two families of fungi are responsible: Trichophyton and Microsporum. Globally, Microsporum canis is the most common culprit, accounting for about 52% of confirmed cases in children between 2020 and 2023. Trichophyton tonsurans and Trichophyton violaceum are the next most frequent species, and which one you’re dealing with depends largely on where you live and what animals you’re around.
These fungi feed on keratin, the protein that makes up hair and the outer layer of skin. Some species invade the outside of the hair shaft, destroying its outer coating. Others burrow inside the shaft, leaving the surface intact but weakening the hair from within until it snaps. This distinction matters for diagnosis, since the two types behave differently under special lights and microscopes, but from your perspective the symptoms overlap considerably.
How It Spreads
Scalp fungus spreads through three main routes: direct contact with an infected person, contact with an infected animal, or touching contaminated objects. Cats and dogs are common carriers of Microsporum canis, and transmission can happen through casual petting. Even animals that look healthy can carry the fungus without obvious symptoms, so clinicians recommend considering all animal contacts as a potential source.
Shared combs, brushes, hats, pillowcases, and headrests can all harbor fungal spores. The spores are hardy and can survive on surfaces for weeks to months. This is why outbreaks sometimes ripple through households or classrooms. Reducing transmission means not sharing personal hair items, regularly cleaning brushes and surfaces, and washing textiles that contact the head.
What It Looks and Feels Like
The hallmark sign is one or more round, scaly patches on the scalp where hair has broken off. These patches tend to expand slowly over time. Up close, the scalp in these areas looks silvery and flaky, and you may notice tiny black dots scattered across the patch. Those dots are the stumps of hairs that snapped right at the skin surface.
Other common signs include:
- Brittle hair that breaks or pulls out easily
- Tender or painful spots on the scalp
- Itching that ranges from mild to intense
- Scaling that can resemble severe dandruff
Children are affected far more often than adults, though adults can get it too, particularly those with weakened immune systems.
Kerion: The Inflammatory Complication
In some cases, the immune system mounts an aggressive response to the fungus, producing a kerion. This is a large, boggy, pus-filled swelling on the scalp that oozes from the hair follicles. It can be quite painful, and it sometimes comes with fever and swollen lymph nodes in the neck. A kerion is often mistaken for a bacterial abscess because the two look similar.
The real danger with a kerion is scarring. Without treatment, the intense inflammation can permanently destroy hair follicles, leaving patches of irreversible hair loss. The longer a kerion goes untreated, the higher the risk of permanent damage. If you notice a soft, swollen, pus-draining mass on your or your child’s scalp, getting it evaluated quickly matters.
How It Differs From Other Scalp Conditions
Scalp fungus is frequently confused with seborrheic dermatitis (dandruff) and scalp psoriasis, since all three cause flaking and itching. A few features help distinguish them.
Scalp fungus produces distinct round patches of hair loss with broken hair stubs or black dots. Dandruff and psoriasis don’t typically cause hair to break off in well-defined circles. Psoriasis scales tend to be thicker and drier, and psoriasis often extends beyond the hairline onto the forehead or behind the ears. It also usually shows up elsewhere on the body, such as the elbows, knees, or lower back, and can cause pitting in the nails. Seborrheic dermatitis produces greasier, yellowish scales and tends to affect areas with high oil production. Neither dandruff nor psoriasis involves fungal invasion of the hair shaft, and neither is contagious.
How It’s Diagnosed
A doctor can often suspect scalp fungus from its appearance, but confirming the diagnosis usually involves one or more tests. The simplest is a Wood lamp exam, where a special ultraviolet light is shone on the scalp in a dark room. Hairs infected with certain Microsporum species glow bright green to yellow-green. However, Trichophyton tonsurans, one of the most common species in North America, does not fluoresce at all, so a negative Wood lamp result doesn’t rule out infection.
For a more definitive answer, doctors pluck a few affected hairs and examine them under a microscope after softening them in a potassium hydroxide solution. This reveals fungal structures around or inside the hair shaft. A fungal culture, which takes a few weeks to grow, can identify the exact species and help guide treatment choices.
Treatment Requires Oral Medication
This is the single most important thing to understand about scalp fungus: topical treatments alone don’t work. Antifungal creams, ointments, and shampoos cannot penetrate into the hair shaft where the infection lives. The American Academy of Family Physicians specifically advises against treating tinea capitis with topical medications only.
Oral antifungal medication is the standard treatment. Griseofulvin is typically considered first-line, especially when the exact fungal species is unknown. Treatment generally lasts four to six weeks, though infections caused by certain Microsporum species may require a longer course. Terbinafine is also FDA-approved for scalp fungus and is sometimes preferred depending on the species involved. Other options like fluconazole (typically given for about six weeks) or itraconazole are used less commonly.
Medicated shampoos containing ketoconazole or selenium sulfide are often recommended alongside oral medication. They won’t cure the infection on their own, but they reduce the number of viable fungal spores on the scalp’s surface. This can shorten recovery time and, importantly, make you less likely to spread the fungus to others while the oral medication does its work.
What to Expect During Recovery
Improvement is gradual. Scaling and inflammation typically begin to ease within the first two weeks of oral treatment, but hair regrowth takes longer. The full treatment course of four to six weeks (or more) needs to be completed even if symptoms improve earlier, because stopping too soon allows the fungus to return.
Hair that was lost from non-scarring patches generally grows back once the infection clears. Hair lost from a kerion may or may not return, depending on how much follicle damage occurred before treatment started. During treatment, using the medicated shampoo as directed and avoiding sharing hair tools or headwear helps prevent reinfection and protects household members.
Household contacts, especially children, should be checked for signs of infection. Pets that may be carrying the fungus should be evaluated by a veterinarian, since reinfection from an untreated animal source is common even after successful treatment.