Dermatophytid; Dermatophyte fungal infection - tinea; Tinea
Ringworm is a skin infection due to a fungus. Often, there are several patches of ringworm on the skin at once. The medical name for ringworm is tinea.
Ringworm is common, especially among children. But, it can affect people of all ages. It is caused by a fungus, not a worm like the name suggests.
Many bacteria, fungi, and yeast live on your body. Some of these are useful, while others can cause infections. Ringworm occurs when a type of fungus grows and multiplies on your skin.
Ringworm can spread from one person to another. You can catch ringworm if you touch someone who has the infection, or if you come in contact with items contaminated by the fungus, such as combs, unwashed clothing, and shower or pool surfaces. You can also catch ringworm from pets. Cats are common carriers.
The fungus that causes ringworm thrive in warm, moist areas. Ringworm is more likely when you are often wet (such as from sweating) and from minor injuries to your skin, scalp, or nails.
Ringworm can affect the skin on your:
Habif TP. Superficial fungal infections. In: Habif TP, ed. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 6th ed. Philadelphia, PA: Elsevier; 2016:chap 13.
Hay RJ. Dermatophytosis (ringworm) and other superficial mycoses. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, Updated Edition. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 268.