What Causes Ringworm?

Ringworm, caused by microscopic skin fungus called dermatophytes, leads to a ring-shaped rash. No actual worm is involved in this infection.

Ringworm is a skin condition caused by dermatophytes, a type of fungus that lives on the dead outer layer of skin. The condition called “ringworm” because it can cause a circular rash shaped like a ring. There is no worm involved. 

Ringworm is named based on where it affects the body: 

• Groin — tinea cruris (also called “jock itch”)
• Feet — tinea pedis (also called “athlete's foot”)
• Scalp — tinea capitis
• Body — tinea corporis
• Beard — tinea barbae

Ringworm affects the skin, fingernails, and toenails. Symptoms of ringworm appear within 4 days to 2 weeks after coming into contact with the fungi that cause ringworm.

Symptoms of ringworm include:

• Ring-shaped rash
• Skin redness
• Scaly, cracked skin
• Skin swelling
• Itching
• Hair loss/bald spot
• Blisters

Ringworm 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 (such as household pets).

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

Body and groin — tinea corporis and cruris (“jock itch”) treatment includes: 

• Over-the-counter (OTC) 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 (OTC) antifungal products
• Chronic or extensive tinea pedis may require oral antifungals
  • Terbinafine
  • Itraconazole
  • Fluconazole
• Chronic tinea pedis may require adjunctive therapy such as foot powder or talcum powder to prevent skin softening

Scalp — tinea capitis treatment includes:

• 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