Ringworm is not a worm at all. It’s a common fungal infection of the skin that gets its name from the circular, ring-shaped rash it produces. The fungi responsible feed on keratin, the protein that makes up the outer layer of your skin, hair, and nails. Ringworm is highly contagious, but it’s also straightforward to treat in most cases.
What Causes Ringworm
Three groups of fungi cause ringworm: Epidermophyton, Microsporum, and Trichophyton. These are molds that can only survive by consuming keratin, which is why they’re limited to infecting the skin’s surface, hair, and nails rather than deeper tissues. They thrive in warm, moist environments, which is why infections are more common in skin folds, sweaty areas, and during humid weather.
How It Spreads
You can pick up ringworm through direct skin contact with an infected person or animal, or by touching contaminated objects like towels, bedding, combs, or gym equipment. Pets, especially cats and dogs, are a common source. Symptoms typically appear 4 to 14 days after contact with an infected animal, its fur, or a contaminated surface.
The fungus sheds in tiny skin flakes and bits of fur, which can linger on surfaces. Regular cleaning of shared items and pet bedding helps remove these traces and reduces the chance of spreading the infection to other household members or animals.
What Ringworm Looks Like
The hallmark sign is a red, itchy, ring-shaped rash with a clearer or scaly center. The ring itself is slightly raised, and the area inside it may contain scattered bumps. On lighter skin, these bumps appear red. On darker skin tones, they can look red-purple, brown, gray, or black. Some people develop overlapping rings.
The rash can appear almost anywhere on the body, and doctors use different names depending on the location:
- Body (tinea corporis): The classic ring-shaped rash on the trunk, arms, or legs.
- Scalp (tinea capitis): Itchy, scaly patches on the head that can cause circular bald spots. Without treatment, these spots grow larger and multiply.
- Feet (athlete’s foot): Itching, burning, and cracked skin between the toes.
- Groin (jock itch): An itchy, burning rash in the groin and inner thigh area.
- Beard area (tinea barbae): Infection in the facial hair region, more common in men who work with animals.
- Nails: Thickened, discolored, brittle nails that can take months to clear.
Conditions That Look Similar
Several skin conditions mimic ringworm’s circular shape, which can lead to misdiagnosis and ineffective treatment. Nummular eczema, for example, also produces coin-shaped patches on the skin, but it’s an inflammatory condition rather than a fungal infection. One useful clue: ringworm tends to show up as one or two isolated patches, while nummular eczema often causes multiple patches at once. Psoriasis can also create scaly, reddish plaques, but these are usually thicker, more silvery, and don’t have the distinctive clear center that ringworm produces.
If an over-the-counter antifungal cream doesn’t improve the rash within a couple of weeks, there’s a good chance it isn’t ringworm. A doctor can confirm the diagnosis with a simple skin scraping examined under a microscope or sent to a lab for culture.
How Ringworm Is Treated
Treatment depends on where the infection is. Ringworm on the body responds well to antifungal creams, ointments, or powders applied directly to the skin for 2 to 4 weeks. Several effective options are available without a prescription, including clotrimazole (Lotrimin), miconazole, terbinafine (Lamisil), and ketoconazole. Apply the cream to the rash and a margin of healthy skin around it, and keep using it for the full recommended duration even if the rash clears up early. Stopping too soon is one of the most common reasons ringworm comes back.
Scalp ringworm is harder to treat because the fungus burrows into hair follicles where topical creams can’t reach. It requires prescription antifungal pills taken by mouth for 1 to 3 months. Nail infections also need oral medication and are the slowest to resolve, sometimes taking several months to a year for the infected nail to fully grow out and be replaced by healthy nail.
How Long You’re Contagious
An untreated ringworm infection remains contagious for as long as the rash is present. Once you start antifungal treatment, you’re generally no longer contagious after about 48 hours. During that window, avoid sharing towels, clothing, or bedding, and cover the rash if possible. If your pet is the source, they’ll need treatment too, and you should clean any surfaces or bedding they’ve been in contact with to prevent reinfection.