Lyme disease is an inflammatory disease spread through a tick bite. Symptoms Rash: A small, red bump may appear within a few days to a month, often at the site of the tick bite "” often in your groin, belt area or behind your knee. It may be warm to the touch and mildly tender. Over the next few days, the redness expands, forming a rash that may be as small as your fingertip or as large as 12 inches (30 centimeters) across. It often resembles a bull's-eye, with a red ring surrounding a clear area and a red center. The rash, called erythema migrans, is one of the hallmarks of Lyme disease, affecting about 70 percent to 80 percent of infected people. If you're allergic to tick saliva, redness may develop at the site of a tick bite. The redness usually fades within a week. This is not the same as erythema migrans, which tends to expand and get redder over time. Migratory joint pain: If the infection is not treated, you may develop bouts of severe joint pain and swelling several weeks to months after you're infected. Your knees are especially likely to be affected, but the pain can shift from one joint to another. Neurological problems: In some cases, inflammation of the membranes surrounding your brain (meningitis), temporary paralysis of one side of your face (Bell's palsy), numbness or weakness in your limbs and impaired muscle movement may occur weeks, months or even years after an untreated infection. Memory loss, difficulty concentrating and changes in mood or sleep habits also can be symptoms of late-stage Lyme disease. Less common signs and symptoms: Some people may experience heart problems, such as an irregular heartbeat, several weeks after infection, but this rarely lasts more than a few days or weeks. Eye inflammation, hepatitis and severe fatigue are possible as well.