What Are the Common Causes of a Circular Skin Rash?

A group of fungal infections, collectively known as ringworm, are the most common cause of circular or ring-shaped skin rashes. These infections result from a type of fungus known as tinea and may affect the scalp, beard, groin, feet or body. Ringworm takes on different names depending on the affected body part, according to MedlinePlus, but on the feet, it is tinea pedis, or athlete's foot, and on the groin, it is tinea cruris, or jock itch.

The classic sign of ringworm is a red ring of small blisters or scaly skin. The skin inside the ring sometimes heals as the infection grows larger. It is more common among children, in whom it spreads with the sharing of hats, combs and other personal items. It can also spread through sharing towels and sports equipment, according to WebMD.

The most common way to catch ringworm is from another human, but the disease also passes from animals to humans, according to KidsHealth. The fungus can pass from direct contact with another person with ringworm or from a moist shower floor. Showering after playing a contact sport, washing the hands after touching pets and wearing shower shoes in public showers can help to prevent contracting the disease.

Doctors treat most ringworm with topical medications. If it affects the scalp or nails, they usually prescribe oral medication, as KidsHealth reports.