They also had specific names for the same infection found in the groin, armpit, facial hair, or nails. It was not until 1837 that the true cause of ringworm was found. Over the next several years, a number of investigators proved that what we call ringworm is always a fungal infection. This was the first time that any microscopic organism was ever proven to cause human disease. It has no connection at all with worms, other than the similar appearance of the skin lesions.
Fungi are tiny plants that survive by eating plant or animal material.
These fungi thrive best on skin that is moist, hot, and hidden from the light. Up to 20 percent of the population has one of these infections at any given moment. Ringworm is very mildly contagious. 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.