Ringworm of the body is just one of a number of diseases caused by the group of fungi known as dermatophytes. Other dermatophyte infections include jock itch and athlete's foot. The opportunistic dermatophyte fungus is microscopic, small enough to be carried on the wind. Dermatophytes live on a variety of hosts, including on humans, pets and in soil, and also on objects such as combs and towels until they find a suitable host.
Rash
In order to infect a host, the fungus needs access into the top layer of skin. The skin, which has both an acid barrier and a physical barrier made up of a layer of dried, dead skin cells, usually does a fine job of keeping out pathogens, including dermatophytes. When the skin is injured, cut or torn, the fungus can enter. It colonizes the layer of dead skin cells, where it metabolizes keratin, a protein found in those cells as well as in hair and nails. It causes an itchy, red rash, usually circular or ringed in shape. Dr. Barry L. Hainer, of the Medical University of South Carolina, explains that the rash often has an edge of crusted, scaling skin, called an active border, with central clearing. Some ringworm rashes also blister.
Secondary Infections
Just as dermatophytes need a break in the skin's protective barriers to infect a host, so do other pathogens. A ringworm rash causes large areas of injured skin where secondary infections can occur. Medline Plus notes that bacterial skin infections are common complications of ringworm. Staphylococcus and streptococcus bacteria, which reside on normal, healthy skin but need a cut or injury in order to infect the skin, can cause skin to become red, hot and painful.
Hair Loss
American Family Physicians reports that ringworm of the scalp, which is medically referred to as tinea capitis, is the most common form of ringworm infection in children. There, the rash shows up as red or gray circular patches. Hair loss is common as the dermatophytes metabolize the keratin in the hair shaft, thereby weakening and breaking the hair off. If the infection is severe, a condition called kerion can occur. Mayo Clinic points out that kerion is a severe, painful inflammation of the scalp. Pus-filled sores can form and, when they drain, cause a thick, yellow crust. Kerion can cause scarring and permanent hair loss.
