Sporotrichosis: An infection caused by the fungus Sporothrix schenckii, typically involving the skin. Persons handling thorny plants, sphagnum moss, or baled hay are at increased risk of developing sporotrichosis. The first sign is usually a small painless bump resembling an insect bite. The bump can be red, pink, or purple in color, and it usually appears on the finger, hand, or arm, where the fungus first entered through a break on the skin. This is followed by one or more additional bumps that open and may look like boils. Eventually, the bumps turn into open hollowed-out sores (ulcerations) that are very slow to heal. The infection can also spread to other areas of the body. Treatment is with antibiotics.