The term ringworm is a complete misnomer since the condition is caused by fungi of several different species and not at all by parasitic worms. The name was adopted due to the shape of the infection and had no basis in science. The fungi that cause parasitic infection (dermatophytes) feed on keratin, the material found in the outer layer of skin, hair, and nails but are certainly not worms. These fungi thrive on skin that is warm and moist, but may also survive directly on the outsides of hair shafts or in their interiors. In pets, the fungus responsible for the disease survives in skin and on the outer surface of hairs.
Ringworm infections have been prevalent since before 1906, at which time ringworm was treated with compounds of mercury or sometimes sulfur or iodine. Hairy areas of skin were considered too difficult to treat, so the scalp was treated with x-rays and followed up with anti-parasitic medication. Modern science has allowed us to figure out that a simple anti-fungal topical solution is more than sufficient to treat even the most irritating infections.