A scalp infection is any condition where fungi, bacteria, or viruses invade the skin, hair follicles, or hair shafts on your head, causing symptoms that range from itchy, flaky patches to painful, pus-filled sores. Fungal infections are the most common type, particularly in children ages 3 to 14, but bacterial scalp infections affect people of all ages. While most scalp infections clear up with proper treatment, some can lead to permanent hair loss if left untreated.
Types of Scalp Infections
Scalp infections fall into a few main categories based on what’s causing them: fungi, bacteria, or (less commonly) viruses. Each type looks and behaves differently, and knowing which one you’re dealing with determines how it gets treated.
Fungal Infections
The most well-known fungal scalp infection is tinea capitis, commonly called scalp ringworm. Despite the name, no worm is involved. It’s caused by a group of fungi called dermatophytes that feed on the protein in skin and hair. The infection usually starts as small red bumps that gradually expand into round, scaly patches. Hair in the affected area often breaks off at the surface, leaving short stubble or bald spots. In its classic “black dot” form, broken hairs leave dark dots visible against the scalp.
Another common fungal culprit is a yeast called Malassezia, which naturally lives on everyone’s scalp but can overgrow and cause problems. Malassezia overgrowth is linked to dandruff and a condition called Malassezia folliculitis, where the yeast invades individual hair follicles and creates small, itchy bumps. A rarer type of fungal hair infection called piedra produces tiny hard nodules along the hair shaft itself, either black or white depending on the species involved.
Bacterial Infections
Bacterial scalp infections most often take the form of folliculitis, where individual hair follicles become infected and form small, pus-filled bumps surrounded by red, inflamed skin. The bacterium Staphylococcus aureus is the usual cause, including antibiotic-resistant strains (MRSA). Bacterial folliculitis can develop on its own or as a secondary infection on top of an existing skin condition. If folliculitis deepens, it can form furuncles (boils), which are larger, more painful lumps beneath the skin.
Symptoms to Recognize
The signs of a scalp infection vary depending on the type, but several symptoms overlap. Itching is nearly universal. Redness, flaking, and scaling are common across both fungal and bacterial infections, which is one reason scalp infections are frequently mistaken for dandruff or seborrheic dermatitis at first.
With fungal infections like tinea capitis, you’ll typically see one or more round patches where the scalp looks scaly or irritated, especially at the edges, with the center appearing more normal. Hair loss within those patches is a hallmark sign. The infection can spread to cover large portions of the scalp if untreated, and it sometimes extends to the eyebrows or eyelashes.
Bacterial folliculitis looks different. Instead of large scaly patches, you’ll see clusters of small pustules, each centered around a hair. The surrounding skin is red and tender. If these worsen into boils, the area becomes swollen, warm, and quite painful.
One key way to tell a scalp infection apart from regular dandruff: dandruff causes widespread flaking but doesn’t cause hair loss, round bald patches, or pus. If your scalp is painful, swollen, draining fluid, or losing hair in patches, an active infection is more likely than simple dandruff.
How Scalp Infections Are Diagnosed
A visual exam is often the starting point, but several infections look similar on the surface, so additional testing helps pin down the cause. For suspected fungal infections, a provider may gently scrape some skin or pull a few hairs from the affected area and examine them under a microscope after applying a solution that makes fungal structures easier to see.
A Wood’s lamp, which emits ultraviolet light, can help identify certain fungal species. Hairs infected by specific fungi glow green or yellow-green under the lamp. In a study of 50 children, this method correctly identified Microsporum canis infections with 100% specificity, meaning it rarely produces false positives. However, the most common fungal strain in the United States, Trichophyton tonsurans, does not fluoresce, so a negative Wood’s lamp result doesn’t rule out ringworm. A fungal culture, which takes a few weeks to grow, provides the most definitive answer.
Treatment for Fungal Scalp Infections
Fungal scalp infections require oral prescription medication. Topical antifungal creams, lotions, and powders do not work for scalp ringworm because the fungus lives inside the hair follicle and shaft, where surface treatments can’t reach. According to the CDC, oral antifungal treatment typically lasts 1 to 3 months.
Your provider will choose from a few oral medications based on the specific fungus involved, your age, and other health factors. The course of treatment can feel long, but stopping early often leads to the infection coming back. Medicated shampoos are sometimes used alongside oral medication, not as a cure but to reduce the amount of fungus on the scalp’s surface and lower the chance of spreading it to others.
Treatment for Bacterial Scalp Infections
Mild bacterial folliculitis often responds to topical antibiotic ointments applied directly to the affected spots. A benzoyl peroxide wash used for 5 to 7 days is another option for mild cases. When the infection covers a larger area or doesn’t respond to topical treatment, oral antibiotics taken for about 10 days are the next step. If boils develop despite initial treatment, a combination of oral antibiotics may be needed, and in some cases the boils require draining.
When Infections Lead to Hair Loss
Most scalp infections, when caught and treated early, resolve without permanent damage. Hair grows back once the infection clears. The exception is when a fungal infection triggers an intense inflammatory response called a kerion, a thick, boggy, swollen area of the scalp that oozes pus and forms crusts. A kerion develops because the immune system mounts an aggressive attack against the fungus, and the resulting inflammation can destroy hair follicles in the process.
Kerions are painful and often accompanied by swollen lymph nodes in the neck. Because the inflammation damages the follicle itself, hair loss from a kerion can be permanent, leaving scar tissue where hair once grew. This is one of the main reasons early treatment matters. A similar but rarer pattern called favus involves deep, oozing nodules and abscesses that can also lead to scarring.
Who Gets Scalp Infections
Tinea capitis is overwhelmingly a childhood condition, most common between ages 3 and 14. Children in close-contact settings like schools, daycare, and sports teams are especially vulnerable because the fungi spread easily through shared items and direct contact. Adults can develop it too, particularly those with weakened immune systems, but it’s far less common.
Bacterial folliculitis, on the other hand, affects all age groups. Anything that damages or irritates the hair follicle, such as tight hairstyles, frequent shaving, heavy sweating, or occlusive headwear, increases the risk. People with existing skin conditions like eczema or dermatitis are also more prone to bacterial scalp infections because broken skin provides an entry point for bacteria.
Prevention
The CDC recommends several straightforward hygiene measures to reduce your risk of scalp infections. Don’t share combs, brushes, hats, towels, or pillowcases with others, especially during an active infection. Wash your hands regularly, particularly after touching animals (pets are a common source of Microsporum canis). If someone in your household has a scalp infection, machine wash their clothes, pillowcases, and towels using hot water and a high-heat dryer cycle.
Keeping the scalp clean and dry also helps, since both fungi and bacteria thrive in warm, moist environments. If you’re prone to folliculitis, avoid tight headwear for extended periods and resist the urge to scratch or pick at bumps, as breaking the skin can introduce bacteria or worsen an existing infection.