Cause
Ringworm infection is caused by a
fungus. Fungi (plural of fungus) that cause ringworm
live and multiply on the outer layer of skin. Ringworm is not caused by a worm
or other parasite.
Fungi are present everywhere in our environment, including on the
human body. They thrive in warm, moist areas, such as locker rooms and swimming
pools, and in skin folds. You can get ringworm of the skin by sharing
contaminated towels, clothing, and sports equipment, and by direct contact with
an infected person. Ringworm is common among wrestlers, probably because of the
skin-to-skin contact.1
Ringworm of the skin (tinea corporis) is most commonly caused by
the fungus Trichophyton rubrum, which spreads from one
person to another. It can also be caused by Microsporum
canis, which is spread by cats and dogs. This type is less common but
causes more severe infection.
People often get ringworm of the groin ("jock itch") by
accidentally spreading
athlete's foot fungus to their own groin area. People
with athlete's foot also commonly spread it to their hands (tinea
manuum).
Some people are more likely to get (susceptible to)
fungal infections than others. The tendency to get fungal skin infections or to
have them return after treatment seems to run in families.