Dermatophytosis, more commonly known as as ringworm, is a fungal infection of the skin. Ringworm is a misnomer. The infection isn't caused by a worm. It's caused by a fungus. Ringworm infection can affect both humans and animals. The infection initially presents itself with red patches on affected areas of the skin and later spreads to other parts of the body. The infection may affect the skin of the scalp, feet, groin, beard, or other areas.