Lyme disease initially affects the skin, causing an expanding reddish rash similar to a target or bull's-eye.
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Phase 1: Early localized disease
The site where the tick bites the body is where the bacteria enter through the skin. Within days to weeks of the tick bite, the local skin around the bite develops an expanding ring of flat redness. There may be an outer ring of brighter redness and a central area of clearing, leading to a bull's-eye or target appearance. This classic initial rash is called "erythema migrans." Multiple secondary lesions can occur that are a reaction to the infection and are not due to multiple tick bites. Patients often can't recall the tick bite (the ticks can be as small as the periods in this paragraph). Also, they may not have the identifying rash to signal the doctor. More than one in four patients never develops a rash. The redness of the skin is often accompanied by generalized fatigue, muscle and joint stiffness, swollen glands, and headache resembling symptoms of a viral infection. Later, it can produce abnormalities in the joints, heart, and nervous system.