The name ringworm survives from antiquity when doctors thought that this round rash was indeed caused by a worm. Now we know that this common skin infection has nothing at all to do with worms, but it can have something to do with pets!
Ringworm is a fungal infection of the skin. Fungi survive by eating plant or animal material. The fungi feed on keratin, the material found in the outer layer of skin, hair, and nails. These fungi thrive best on skin that is moist, hot, and hidden from the light. When this infection is found on the feet, it is commonly called athlete’s foot; when it is found in the groin, it is commonly called jock itch; and when it is found on the body, it is still called ringworm.
Up to 20 percent of the population has one of these infections at any given moment. To catch ringworm, you have to be exposed to it and you have to be susceptible. Some people are much more susceptible than others. Those with eczema or other skin problems get ringworm more easily because the protective barrier of the skin’s outer layer is less intact. Children are more susceptible before puberty. Boys get it more easily than girls. Some people are genetically predisposed and can get it easily throughout life.
The classic ringworm rash begins as a dry, raised, round patch, which may be slightly red. The patch may also be somewhat itchy. As it grows, the center of the patch clears, leaving a ring-like appearance. Not all children display this central clearing. In fact, there is wide variability in the way it can appear from person to person.
Ringworm is moderately contagious. Ringworm can be caught from other humans, both by direct contact and by prolonged contact with flakes of shed skin (from sharing clothes or from house dust, for instance). Wrestlers commonly spread it back and forth with their sweaty contact (it’s called tinea gladiatorum!).
It can be caught from domestic animals (especially dogs and cats), as well as most farm animals. The infection can be caught from the animal directly, or from anything, the animal rubs against.
Without treatment, most cases of ringworm would disappear on their own within several months, but they can become chronic.
Ringworm symptoms usually disappear quickly with treatment, but the treatment may need to be continued for two to four weeks to eliminate all of the fungus.
Ringworm is often diagnosed by the history and physical examination (and rapid response to treatment). The diagnosis can be confirmed by looking at skin scrapings under the microscope, where the fungus is visible. Also, ringworm lesions usually do not glow under ultraviolet light.
When apparent ringworm does not respond to treatment as expected, it is important to reconsider the diagnosis.
The treatment for ringworm is one of many effective topical antifungal creams, such as miconazole or clotrimazole. Several of these antifungal creams are now available without a prescription. Treatment may require several weeks. Only by treating for at least one week after the resolution of symptoms can one guarantee eradication. As soon as treatment has begun it’s fine for your child to play with others, but it’s best not to share clothing or to let other children rub the patch of ringworm.
When fungus is found in the nails or on the scalp, the infection is much more difficult to eliminate. Prolonged treatment with a prescription oral anti-fungal medicine, as well as other topical medicines, is usually necessary. Scalp ringworm is a major cause of hair loss.
If you think your pet may be involved, contact your veterinarian to get up-to-date information on the best treatment for animals.
Avoiding exposure is the best way to prevent ringworm. Because these fungi thrive best on skin that is moist, hot, and hidden from the light, dressing to keep the skin cool, dry, and light can also help prevent this infection.