Ringworm is a superficial fungal infection. It is caused by a group of fungi called dermatophytes. These microscopic organisms have a unique ability to live on and digest keratin, the tough, waterproof protein that is the primary structural component of our skin’s outermost layer, our hair, and our nails.

The classic “ring” shape that gives the infection its name is a direct result of how the fungus grows on the skin.

• A helpful analogy is to think of the outer layer of your skin as a vast, dry field of “thatch” (keratin).
• The dermatophyte fungi are like tiny, microscopic “garden pests” that thrive by eating this thatch.
• When fungal spores land on a patch of skin, they begin to grow, multiplying and spreading outward in a circle as they consume the keratin for food.
• The body’s immune system detects this invasion at the leading edge of the circle and sends inflammatory cells to fight it off. This immune response is what creates the red, raised, and often scaly border of the ring.
• The area in the center of the ring often begins to heal and look clearer as the fungi move outward in search of new “thatch” to eat.
• This process of the fungus expanding in a circle with inflammation at its active edge is what creates the characteristic ring-shaped lesion.

Ringworm is a broad term that is further classified by the part of the body it affects. The medical name for each type is “tinea” followed by the Latin term for its location.

• Tinea Corporis: Ringworm of the body (e.g., on the arms, legs, or trunk).
• Tinea Cruris: Ringworm of the groin, commonly known as “jock itch.”
• Tinea Pedis: Ringworm of the feet, commonly known as “athlete’s foot.”
• Tinea Capitis: Ringworm of the scalp, most common in children.
• Tinea Manuum: Ringworm of the hands.
• Tinea Barbae: Ringworm of the beard area.
• Tinea Unguium: Fungal infection of the nails, also known as onychomycosis.

In my experience, many patients are surprised to learn that ringworm isn’t caused by a worm at all, it’s actually a fungal skin infection.

The sole cause of ringworm is an infection with one of several different species of dermatophyte fungi. The three main genera, or groups, of fungi responsible for the infection are Trichophyton, Microsporum, and Epidermophyton. These fungi thrive in warm, moist, and humid environments.

In my experience, it spreads easily through direct skin contact, shared personal items, or contaminated surfaces especially in warm, humid environments.

Ringworm is highly contagious and spreads easily through several routes.

• Human-to-Human (Anthropophilic): This is a very common mode of transmission. It occurs through direct, skin-to-skin contact with a person who has a ringworm infection.
• Animal-to-Human (Zoophilic): A person can contract ringworm by touching or petting an infected animal. Cats and dogs are common sources, as are farm animals like cattle. Ringworm from an animal source often causes a more inflammatory reaction in humans.
• Object-to-Human (Geophilic): The fungal spores can live for a long time on contaminated surfaces and objects, known as fomites. This is another major route of transmission. A person can get infected by touching:
  • Contaminated clothing, towels, or bed linens.
  • Contaminated hairbrushes, combs, or hats.
  • Contaminated surfaces in damp, communal areas like locker room floors, public showers, or pool decks.

In my experience, I see it most often in athletes, children, and people who use communal showers or gyms, where contact with infected surfaces is common.

The signs and symptoms of a ringworm infection vary depending on the location of the rash.

Tinea Corporis (Body Ringworm)

• This is the classic presentation of a ring-shaped rash.
• It begins as a small, red, itchy, scaly spot.
• It slowly grows outward, forming a circle or an oval.
• The border of the ring is raised, red, and scaly, while the center often becomes clearer, creating the classic “ring” appearance.

Tinea Pedis (Athlete’s Foot)

• Itchy, scaly, and peeling skin, most commonly in the moist space between the toes.
• It can also present as dryness and scaling on the soles of the feet, or as painful blisters.

Tinea Cruris (Jock Itch)

• A red, itchy, half-moon-shaped rash in the skin folds of the groin, inner thighs, and buttocks.
• The border is often sharply defined and may have small blisters.

Tinea Capitis (Scalp Ringworm)

This is most common in pre-pubertal children and requires special attention.

• It often presents as one or more round patches of scaly skin and hair loss on the scalp.
• The hairs within the patch may be broken off at the surface, leaving small “black dots.”
• In some cases, the immune system can mount a very intense inflammatory response to the fungus, creating a boggy, swollen, pus-filled mass on the scalp known as a kerion. A kerion can be painful and can lead to permanent scarring and hair loss if not treated aggressively.

Clinically, I look for scaling, cracking, or pustules around the lesion. In scalp infections, patchy hair loss may be a key finding.

While the ring-shaped rash of tinea corporis is often recognizable, it can be confused with other skin conditions like nummular eczema or granuloma annulare. Therefore, a proper diagnosis from a healthcare provider is important.

• Clinical Examination: In many cases, a doctor can diagnose ringworm based on its characteristic clinical appearance and a history of itching.
• KOH Examination:
• The gold standard and most common method for confirming the diagnosis is a KOH test.
  • A doctor will use a scalpel blade or a glass slide to gently scrape a small sample of scale from the active, red border of the rash.
  • This skin scraping is placed on a microscope slide, and a drop of potassium hydroxide (KOH) solution is added.
  • The KOH dissolves the skin cells, leaving behind only the fungal elements.
  • When examined under a microscope, the doctor can see the characteristic, branching, spaghetti-like fungal structures called hyphae, which confirms the diagnosis of a dermatophyte infection.
• Fungal Culture: In some cases, especially for scalp or nail infections, a sample may be sent to a laboratory to be grown in a culture. This can identify the exact species of fungus, but it can take several weeks to get a result.

Clinically, diagnosis is usually made based on appearance, but I sometimes confirm it with a KOH prep or fungal culture if the presentation is atypical or unresponsive to treatment.

Ringworm is a highly treatable infection. The goal of treatment is to eradicate the fungus and relieve the symptoms. The type of treatment depends on the location and severity of the infection.

1. Topical Antifungal Medications

For ringworm infections on the skin of the body, groin, and feet (tinea corporis, cruris, and pedis), the first-line treatment is a topical antifungal medication.

• These come in the form of creams, lotions, or powders and are available both over-the-counter and by prescription.
• Common active ingredients include clotrimazole, miconazole, ketoconazole, and terbinafine.
• It is crucial to apply the cream not only to the visible rash but also to a one-inch margin of normal-looking skin around it.
• Treatment should be continued for one to two weeks after the rash has completely disappeared to ensure all the fungal spores have been eliminated and to prevent recurrence.

2. Oral Antifungal Medications

Oral systemic medications are essential for treating ringworm of the scalp (tinea capitis) and of the nails (onychomycosis). Topical creams cannot effectively penetrate the hair shaft or the nail plate to kill the fungus.

• The most commonly used oral medications include terbinafine, itraconazole, and griseofulvin.
• Treatment for scalp or nail fungus requires a long course of oral medication, often lasting from six weeks to several months.

3. Hygiene and Environmental Measures

In addition to medical treatment, good hygiene practices are essential to prevent the spread of the infection to other parts of your body or to other people.

• Keep the affected skin clean and dry.
• Do not share towels, clothing, combs, hairbrushes, or other personal items.
• Wash contaminated clothing, bedding, and towels in hot water.
• Wear shower shoes or sandals in public showers, locker rooms, and pool areas to prevent athlete’s foot.
• If the infection may have come from a pet, it is important to have the animal checked by a veterinarian and treated if necessary to prevent reinfection.

Clinically, I advise patients to keep the area clean and dry, avoid sharing personal items, and complete the full course of treatment to prevent recurrence.

Ringworm, despite its misleading name, is a very common and highly contagious fungal infection of the skin. It is not caused by a worm. It is characterized by an itchy, red, ring-shaped rash that is caused by skin-loving fungi called dermatophytes. While the rash can be a persistent and annoying nuisance, it is important to remember that it is a superficial infection that is highly treatable. Most cases of ringworm on the body can be cured with over-the-counter antifungal creams. For more stubborn infections of the scalp or nails, effective oral antifungal medications are available. Clinically, I emphasize prevention through good hygiene, treating pets if needed, and avoiding skin-to-skin contact or contaminated items during outbreaks.

Centers for Disease Control and Prevention (CDC). (2024). Ringworm. Retrieved from https://www.cdc.gov/fungal/diseases/ringworm/index.html

The American Academy of Dermatology (AAD). (n.d.). Ringworm: Overview. Retrieved from https://www.aad.org/public/diseases/a-z/ringworm-overview

The Mayo Clinic. (2022). Ringworm (body). Retrieved from https://www.mayoclinic.org/diseases-conditions/ringworm-body/symptoms-causes/syc-20353780