A bite with a red circle around it may be from a tick that's carrying the bacteria that causes Lyme disease, according to WebMD. The red circle appears approximately one month after the bite and often resembles a bull's-eye. There may be one or more red rings, advises Everyday Health.
If a tick is the culprit and Lyme disease has been contracted, other symptoms may accompany the peculiar looking bite, including fever, fatigue, headache, muscle aches, skin rash and irregular heartbeat. Since the first sign of infection is the circular skin rash at the bite sight, WebMD recommends seeking medical attention at the first sign of a red ring.