Ringworm (also called serpigo) is an infection of the skin, characterized by a reddish to brownish raised or bumpy patch of skin that may be lighter in the center, giving the appearance of a “ring.” Contrary to its name, ringworm is not caused by a worm but by parasitic fungi (Dermatophytosis). It can exist anywhere on the body. Depending on its location, it can also be known as tinea pedis or "athlete's foot" when on the feet, tinea cruris or "jock itch" when on the groin area, tinea corporis when on the body, where it is most commonly referred to as ringworm, or tinea capitis when on the scalp.
Fungi are organisms that survive by eating plant or animal material, those that cause parasitic infection (dermatophytes) 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. Together with the other dermatophytosis, up to twenty percent of the population has one of these infections at any given moment.
Ringworm is mildly contagious. Ringworm is also a common infection in domestic animals, especially farm animals, dogs and cats and even small pets like hamsters or guinea pigs. Humans can contract ringworm from these animals as humans are in close contact with them. Chickens may also be a source, due to the dirty conditions in which many poultry live and in which ringworm may thrive. Ringworm can also 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).
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. Some people are genetically predisposed, and can get it easily throughout life.
The best known sign of ringworm in people is the appearance of two or more red raised itchy patches with defined edges, not unlike the herald rash of Pityriasis rosea. These patches are often lighter in the center, taking on the appearance of a ring with hyperpigmentation around the circumference caused by an increase in melanin. If the infected area involves the scalp or beard area, then bald patches may become evident. The affected area may become itchy for periods of time.
Doctors can diagnose ringworm on sight, or they may take a skin scraping, or in the case of animal ringworm or tinea capitis, examine plucked hairs for fungal elements. This is examined under a microscope, or put on an agar plate in a microbiology laboratory and allowed to grow. Some of the fungi fluoresce under a black light examination, often with a Wood's lamp.
In domestic animals, ringworm can cause a variety of symptoms, but most cases show scaling and patches of hair loss. Some cats can be carriers, but show no symptoms.
Sometimes a ringworm infection may cause skin lesions in a part of the body that is remote from the actual infection. Such lesions are called "dermatophytids". The lesions themselves are fungus-free, and normally disappear upon treatment of the actual infection. The most common example is an eruption in the hands resulting from a fungus infection of the feet. Dermatophytids are essentially a generalized allergic reaction to the fungus.
Topical antifungal drugs containing miconazole (Daktarin, Micatin & Monistat), clotrimazole (Canesten, Hydrozole, Lotrimin AF), terbinafine (Lamisil), butenafine (Lotrimin Ultra), and tolnaftate (Tinactin), many available without a prescription, are used to clear up the infection. Pyrithione zinc, found in Head & Shoulders shampoo, is a very effective treatment for ringworm on the scalp and can be used as a body wash to assist in overall treatment. During the 1920s, thallium was used to treat ringworm in children.
Itching, burning, cracking, and scaling that accompany this condition may prevent effective treatment. Ointments may be mixed with hydrocortisone creams such as Cortaid appear to reduce inflammation, but can allow the infection to spread in an uncharacteristic manner, resulting in a lesion known as tinea incognito. Fungal infections may take a while to clear up, but most ringworm infections should see improvement in a week or two. Treatment is usually continued for two weeks after symptoms disappear to prevent future occurrence. Types affecting the nails or scalp are very difficult to treat due to fungal infection in follicle roots or under the nail itself.
On September 28, 2007, the U.S. Food and Drug Administration approved Terbinafine (Lamisil by Novartis AG) as a new treatment for use by children aged 4 and up. Antifungal granules can be sprinkled on a child's food to treat ringworm of the scalp, Tinea capitis.
Griseofulvin is a traditional drug used to treat ringworm in both animals and people. It can be very effective, but usually requires a prescription and may produce side effects. In cats and cattle, sulfurated lime rinses are often used to treat ringworm; and dilute povidone-iodine may be used as a wash in cattle. Enilconazole, as a rinse, is an effective ringworm treatment available in many countries for treating animals.
Lufenuron, the active ingredient in Program oral flea treatment, is also commonly prescribed by vets to treat ringworm infections in cats and dogs.
In humans, if ringworm infections are left untreated, it may spread to other areas of the body. This can result in complications such as bacterial infections, dermatitis, other skin disorders and/or scarring of affected areas.
Fungi thrive in warm, moist areas, such as locker rooms and swimming pools, and in skin folds. The fungi may be present without any symptoms.
Advice often given to prevent ringworm includes: