Ringworm is a skin infection that is characterized by itchy, scaly patches on the skin, fingernails, and scalp. Ringworm of the feet is known as athlete’s foot, and ringworm of the groin is known as jock itch. Interestingly, and contrary to popular belief, ringworm is not a worm but a disease caused by a fungus. It was originally named based on the belief that it was caused by a wormlike parasite.
Species Name: Various species of Microsporum or Trichophyton fungi
Type of Microbe: Fungus
How it Causes Disease: The fungi attach and grow on keratin-containing cells, such as those found in the skin, near the hair and fingernails.
How it Spreads: There are several ways that people can get infected with ringworm. Ringworm most commonly spreads from person-to-person through skin contact or contact with contaminated personal items. Ringworm can also be spread through pets, especially cats and dogs. Other animals, including cows, goats, pigs, and horses can also spread ringworm to people. Finally, rare cases of ringworm occur through environmental sources. These cases tend to be more frequent in gardeners or agricultural workers who come in contact with the fungi in soil.
Who’s at Risk? Ringworm is very common among children, but it can affect all people. Scalp ringworm more frequently affects young children and school athletes, whereas ringworm on the body has occurred in children with young pets and in outbreaks among high school wrestling teams.
Symptoms: Ringworm usually begins with a small raised patch that grows into larger, scaly patches with defined edges. The center of the rash eventually clears to produce a ring. It can sometimes be itchy, but is usually not painful. Symptoms of skin infection usually appear 4 to 10 days after exposure. Ringworm of the scalp usually appears 10 to 14 days after exposure.
Diagnosis: Ringworm is diagnosed by appearance, and additional tests are usually not necessary. If confirmation is needed, a special UV light (called a Wood’s lamp) can be used to examine the fungus. Alternatively, a fungal culture or microscopic examination of a skin biopsy can be used.
Prognosis: With proper treatment, ringworm usually resolves within 2 to 4 weeks.
Treatment: Keep skin clean and dry, and apply topical anti-fungal creams -- such as nystatin, terbinafine, clotrimazole, or miconazole -- once or twice every day for 14 to 21 days. If the infection does not resolve with these treatments, antifungal pills may be prescribed.
Prevention: Practice good hygiene; do not share personal items, and keep common areas in gyms, locker rooms, daycares, and schools clean and dry; treat infected pets.
Sources Mims CA, Playfair JH, Roitt, IM, Wakelin D, Williams R, and Anderson RM. Medical Microbiology. ©1993. Mosby-Year Book Europe Limited. London, UK.
Ringworm. MedlinePlus. US National Library of Medicine and the National Institutes of Health.
