What Causes Ringworm Rash?

What Is Ringworm?

Ringworm is a fungal skin infection that produces a characteristic round, ring-shaped rash.
Ringworm is a fungal skin infection that produces a characteristic round, ring-shaped rash.

Ringworm is a skin infection caused by dermatophytes, which are a type of fungus that lives on the dead outer layer of skin. Despite the name, there is no worm involved in the condition. It’s called “ringworm” because it can cause a circular rash shaped like a ring.

Ringworm is often named based on its location on the body: 

What Are Symptoms of Ringworm?

Ringworm affects the skin as well as the fingernails and toenails. The symptoms of ringworm appear between 4 to 14 days after coming into contact with the fungi that cause ringworm.

Symptoms of ringworm can depend on which part of the body is infected, but they usually include:

  • Ring-shaped rash
  • Itching
  • Skin redness
  • Scaly, cracked skin
  • Hair loss

Symptoms of ringworm that are specific to a location on the body:

  • Feet (tinea pedis or “athlete’s foot”):
    • Red, swollen, peeling, itchy skin between the toes 
  • Soles and heels may also be affected
    • Skin on the feet may blister in severe cases
  • Groin (tinea cruris or “jock itch”): 
    • Scaly, itchy, red spots, usually on the inner sides of the skin folds of the thigh
  • Scalp (tinea capitis): 
    • More common in children 
    • Scaly, itchy, red, circular bald spot
    • Bald spot may expand in size and several spots could develop if the infection spreads
  • Beard (tinea barbae): 
    • Scaly, itchy, red spots on the chin, cheeks, and upper neck
    • Spots can become crusted over or filled with pus
    • Affected hair may fall out

What Causes Ringworm?

Ringworm and the characteristic ringworm rash are most often caused by human dermatophytes, a type of fungus transmitted by direct contact with human ringworm sores. Ringworm may also be acquired from the soil or through exposure to animals (commonly household pets).

Risk factors for developing ringworm include:

  • People who have a weakened immune system (such as from HIV/AIDS, cancer, chemotherapy, diabetes, or certain medications)
  • Use of public showers or locker rooms
  • Athletes involved in contact sports, such as wrestling
  • Excessive sweating in tight shoes or clothing
  • Close contact with affected animals such as household pets
  • Working with soil that has ringworm fungus
  • Living in a warm, humid climate
  • Close contact with a person who is infected
  • Sharing bedding, towels, or clothing with a person who is infected

How Is Ringworm Diagnosed?

Ringworm can often be diagnosed with a physical examination of the affected skin. Tests that may be indicated to diagnose ringworm include:

  • Skin scraping to be examined under a microscope or sent to a laboratory for a fungal culture
  • Ultraviolet light (can only diagnose two species: Microsporum canis and audouinii)

What Is the Treatment for Ringworm?

Treatment for ringworm may vary depending on where on the body it occurs.

Body and groin - tinea corporis and cruris (jock itch) treatment includes: 

  • Over-the-counter antifungal products
  • For tinea cruris, keep the groin area clean and dry and wear cotton underwear
  • Extensive or recurrent infections may require systemic antifungal therapy 

Feet - tinea pedis (athlete's foot) treatment includes:

  • Over-the-counter antifungal products
  • Chronic or extensive tinea pedis may require oral antifungals such as terbinafine, itraconazole, or fluconazole
  • Chronic tinea pedis may require adjunctive therapy such as foot powder or talcum powder to prevent skin softening

Scalp - tinea capitis treatment includes:

  • Treatment with systemic antifungal medication (topical antifungal products are ineffective in treating tinea capitis)
    • Griseofulvin 
    • Terbinafine 
    • Itraconazole and fluconazole are considered safe and effective, but are not FDA-approved for tinea capitis 
    • Selenium sulfide shampoos can be used as adjunctive therapy 

What Are Complications of Ringworm?

When treated promptly and thoroughly, ringworm rarely has complications. The main complication of ringworm is that it can spread to other parts of the body.

If the skin becomes scaly and cracked due to ringworm rash, secondary bacterial infection may occur which requires treatment with antibiotics.

How Do You Prevent Ringworm?

  • Keep skin clean and dry, and dry off completely after showering or bathing
  • Don’t go barefoot in locker rooms or public showers
  • Wear loose shoes that allow air to circulate freely around the feet
  • Keep fingernails and toenails clean and trimmed short
  • Do not share clothing, towels, sheets, or personal items with someone who has ringworm
  • Wash hands with soap and water after playing with pets
    • If you suspect your pet has ringworm, take them to a veterinarian
    • Vacuum areas your pet occupies
    • Disinfect surfaces and thoroughly launder pet bedding
  • Athletes involved in close contact sports should shower immediately after practice and keep sports gear clean
  • Athletes should not share sports gear with others
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