Slide show: Poison ivy and other summer skin irritants
Photos of Lyme disease rash
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Lyme disease is a tick-borne illness that causes a distinctive rash, flu-like symptoms and aching joints. The rash begins as a small, red bump (A) that appears within a few days to a month after a tick bite. Over the next few days, the redness expands and may resemble a bull's-eye (B). Fever, chills, fatigue, headache and body aches may accompany the rash.

If you suspect that you've been bitten by a tick and experience signs and symptoms of Lyme disease, contact your doctor immediately. Treatment is most effective if begun early. Left untreated — even if the signs and symptoms resolve on their own — Lyme disease can cause serious complications involving the heart, joints and nervous system.

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