Article on erythema migrans

Erythema migrans is not a reaction to a tick bite, but rather an outward sign of an actual Lyme disease infection in your skin. When the rash first appears, Lyme disease has likely just started to spread through your body, but is still more localized. Erythema migrans is only caused by Lyme disease. Approximately 70% to 80% of people with Lyme disease, which is spread by ticks, will develop erythema migrans. The rash appears where you were bitten by a tick somewhere between 3 and 30 days Trusted Source after the bite. It can spread up to 12 inches across and may be warm to the touch. It's not usually itchy or painful and may appear in more than one place on the body. Untreated Lyme disease can cause: Chronic joint inflammation (Lyme arthritis), particularly of the knee. Neurological symptoms, such as facial palsy and neuropathy. The prognosis for patients with Lyme disease is generally excellent when they are treated early with appropriate antibiotic regimens.