Ringworm: Fungal Cause, Not a Worm—Facts and Treatment

Ringworm (dermatophytosis) is caused by fungi, not worms. The name comes from the characteristic ring-shaped rash.

The Culprit: Dermatophytes

Dermatophytes are molds that feed on keratin—the tough protein in the outer layer of skin, hair, and nails. The three main genera:

• Trichophyton (skin, hair, nails)
• Microsporum (skin, hair)
• Epidermophyton (skin, nails)

Transmission

• Direct skin-to-skin contact (human or animal)
• Fomites: towels, clothing, combs, gym mats, shower floors
• Soil (geophilic species)

Clinical Forms

• Tinea corporis (body): Annular, scaly, erythematous plaques with central clearing.
• Tinea capitis (scalp): Scaling, alopecia, black dots, kerion (inflammatory boggy mass).
• Tinea pedis (athlete's foot): Interdigital maceration, scaling, vesicles.
• Tinea cruris (jock itch): Groin folds, sharp margins.
• Tinea unguium (onychomycosis): Thick, discolored, brittle nails.

Diagnosis

• KOH prep of skin/hair/nail scraping: hyphae visible.
• Fungal culture (species ID, 2–4 weeks).
• PCR (rapid, species-specific).

Treatment

• Topical antifungals (terbinafine, clotrimazole, miconazole): 2–4 weeks for skin.
• Oral antifungals (terbinafine, itraconazole, griseofulvin): Required for scalp, nails, extensive disease.
• Hygiene: Keep area dry, wash bedding/clothing in hot water, treat pets if source.

Prevention

• Avoid sharing personal items.
• Wear sandals in communal showers/pools.
• Dry thoroughly after bathing (especially between toes).
• Treat pets with lesions promptly.

Ringworm is common, contagious, and curable. See a clinician if OTC treatment fails after 2 weeks or if scalp/nails are involved.