Lyme disease is an infection caused by the tick-borne Borrelia burgdorferi bacteria. If untreated, Lyme disease progresses through three stages. During the first early localized stage, a characteristic rash appears at the site of the tick bite in 75 percent of those infected, according to the Merck Manual for Healthcare Professionals. The symptomatic rash may later spread; after it fades, it might recur at a later stage of the disease.
Spot or Bump
One of the early symptoms of Lyme disease is a rash known as erythema migrans. This inflammatory reaction first appears as a flat, red spot on the skin, called a macula, or a red raised bump or pimple, called a papule, according to the Merck manual. This spot or bump occurs at the site of the tick bite, often in the armpit or on the thigh or buttock. It might feel tender and warm to the touch, according to the staff of MayoClinic.com.
Expanding Patch
Between three and 30 days after the original infection, the spot or bump expands to form a red patch with a diameter of five to six inches, according to the U.S. Food and Drug Administration. The center of the patch may clear while the periphery remains red in color, giving the area the appearance of a bull's eye, according to the Merck manual. The center might become hard and darkened. The University of Maryland Medical Center notes that an incomplete circle may form, giving the appearance of an arc rather than a complete ring, and that patients report feeling a burning sensation rather than itchiness at the site of the rash. This usually disappears after three to four weeks.
Secondary Rash
Shortly after the beginning of the infection, almost 50 percent of patents who don't receive treatment for Lyme disease develop several other smaller secondary lesions, the Merck manual notes. This secondary, symptomatic rash appears on other areas of the body, and the lesions do not have hardened centers. The appearance of secondary lesions indicate the dissemination of the Borrelia burgdorferi bacteria from the original infection site to other areas of the body.
Reappearance
During late-stage Lyme disease, skin lesions that have healed may reappear, the Merck manual says.
Allergic Reaction Rash
People who are allergic to the saliva of ticks may experience a reaction and the location of the tick bite may turn red, according to MayoClinic.com. The redness is temporary and doesn't deepen in color or expand, as with erythema migrans.
