Ringworm, known more correctly as dermatophytosis, is a skin infection caused by any of forty or so different types of microbial fungus. It causes inflammation and itchiness, making the skin scaly and forming a circular rash, and sometimes causing hair loss and blistering. Typical infection is by Trichophyton, Microsporum, and Epidermophyton species and is associated with skin contact with other people. Excessive sweating, obesity, and poor immune function are important risk factors.