What group of fungi causes ringworm infections in humans?

The group of fungi that causes ringworm infections in humans is dermatophytes.

Dermatophytes are fungi adapted to digest keratin, the tough protein in the outer layer of skin, hair, and nails. The traditional medically important genera are Trichophyton, Microsporum, and Epidermophyton, although modern taxonomy recognizes a broader group. They usually remain in superficial, nonliving tissues rather than invading deeper living tissue.

“Ringworm” is a misleading name: no worm is involved. The circular appearance comes from outward growth through the outer skin layer, often leaving a more active, scaly edge and clearer center. Different infections receive different names, including tinea corporis for body ringworm, tinea pedis for athlete’s foot, and tinea capitis for scalp infection.

Dermatophytes may spread through contact with infected people, animals, soil, or contaminated objects such as towels, combs, clothing, and floors. A common mix-up is confusing ringworm with yeast infections, but yeasts such as Candida are not dermatophytes. Diagnosis may involve a skin scraping examined with potassium hydroxide, while treatment uses antifungal medicines.