Ringworm, Despite Its Name, Is Not Caused By Worms But Rather By Various Types Of Fungi. The Main Cause Of Ringworm Is Fungal Infection. Fungi That Cause Ringworm Thrive In Warm, Moist Environments And Can Be Passed From Person To Person, Animal To Person, Or Even From Soil To Person. The Fungi Responsible For Ringworm Belong To A Group Called Dermatophytes, Which Have A Predilection For Keratinized Tissues Such As Skin, Hair, And Nails.