Lyme disease signs and symptoms vary widely because Lyme disease can affect various parts of the body. Not everyone with the disease will have all of the signs and symptoms. But in general, Lyme disease can cause:

• 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.
• Flu-like symptoms. A fever, chills, fatigue, body aches and a headache may accompany the rash.
• 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.

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In the United States, Lyme disease is caused by the bacterium Borrelia burgdorferi, which is carried primarily by deer ticks. The ticks are brown and often no bigger than the head of the pin, which can make them nearly impossible to spot.

Ticks feed on blood, attaching to a host and feeding until they're swollen to many times their normal size. During feeding, ticks that carry disease-producing bacteria can transmit the bacteria to a healthy host. Or they may pick up bacteria themselves if the host is infected. In areas where Lyme disease is common, as many as 50 percent of deer ticks may carry Borrelia burgdorferi.

Deer ticks typically feed on the blood of mice, small birds and deer, but they can also feed on the blood of humans, cats, dogs and horses. They live in low bushes and tall grasses of wooded areas, waiting for warmblooded animals to pass by. Deer ticks are most active in the summer.

To contract Lyme disease, you must be bitten by an infected deer tick. The bacteria enter your skin through the bite and eventually make their way into your bloodstream. Before bacteria can be transmitted, a deer tick must take a blood meal and that can take more than 48 hours of feeding. Only ticks that are attached to your skin and are feeding can transmit the bacteria. An attached tick that has a swollen appearance may indicate that enough time has elapsed to transmit bacteria. Removing the tick as soon as possible may prevent infection.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Where you live or vacation can affect your chances of getting Lyme disease. So can your profession and the type of outdoor activities you enjoy. The most common risk factors for Lyme disease include:

• Spending time in wooded or grassy areas. In the United States, deer ticks are most prevalent in the Northeast and Midwest regions and in northwestern states like Oregon and Washington. All have heavily wooded areas where deer ticks thrive. In these regions, children who spend a lot of time outdoors are especially at risk. So are people with outdoor occupations and those who live where mice are common. Deer ticks feed on mice, which are a prime reservoir for Lyme disease bacteria.
• Having exposed skin. Ticks attach easily to bare flesh. If you're in an area where ticks are common, protect yourself and your children by wearing long sleeves and long pants. Don't allow your pets to wander in tall weeds and grasses.
• Not removing ticks promptly or properly. Bacteria from a tick bite can enter your bloodstream only if the tick stays attached to your skin for 48 hours or longer. If you remove a tick within two days, your risk of acquiring Lyme disease is low.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

If you've been bitten by a tick and experience symptoms
Only a minority of deer tick bites lead to Lyme disease. The longer the tick remains attached to your skin, the greater your risk of getting the disease. If you know you've been bitten and experience signs and symptoms of Lyme disease — particularly if you live in an area where Lyme disease is prevalent — contact your doctor immediately. Treatment for Lyme disease is most effective if begun early.

See your doctor even if symptoms disappear
It's important to consult your doctor even if signs and symptoms disappear because the absence of symptoms doesn't mean the disease is gone. Left untreated, Lyme disease can spread to other parts of your body from several months to years after infection — causing arthritis and nervous system problems. Ticks can also transmit other illnesses, such as babesiosis, Colorado tick fever, anaplasmosis and ehrlichiosis.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Lyme disease is frequently overdiagnosed. Its variable signs and symptoms are nonspecific and are often found in other conditions, such as viral infections, various joint disorders, muscle pain (fibromyalgia), chronic fatigue syndrome, and even depression. What's more, the ticks that transmit Lyme disease also can spread other diseases at the same time.

If you don't have the characteristic Lyme disease rash, your doctor may ask detailed questions about your medical history and do a physical exam. Lab tests to identify antibodies to the bacteria may be used to help confirm the diagnosis. These tests are most reliable a few weeks after an infection, after your body has time to develop antibodies. Even then, however, the tests aren't entirely foolproof. They include:

• Enzyme-linked immunosorbent assay (ELISA) test. The test used most often to detect Lyme disease, ELISA detects antibodies to B. burgdorferi. But because it can sometimes provide false-positive results, it's not used as the sole basis for diagnosis.
• Western blot test. If the ELISA test is positive, another test — the Western blot — is usually done to confirm the diagnosis. The Western blot detects antibodies to several proteins of B. burgdorferi.
• Polymerase chain reaction (PCR). This test helps detect bacterial DNA in fluid drawn from an infected joint. It's not effective at detecting infection of blood or urine. It's used for people who may have chronic Lyme arthritis. It may also be used to detect persistent infection in the cerebrospinal fluid of people who have nervous system symptoms.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Left untreated, Lyme disease can cause:

• Chronic joint inflammation (Lyme arthritis), particularly of the knee
• Neurological symptoms, such as facial palsy and neuropathy
• Cognitive defects, such as impaired memory
• Heart rhythm irregularities
• Memory loss
• Difficulty concentrating
• Changes in mood or sleep habits

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

Oral antibiotics
Oral antibiotics are the standard treatment for early-stage Lyme disease. These usually include doxycycline for adults and children older than 8, or amoxicillin or cefuroxime axetil for adults, younger children and pregnant or breast-feeding women. These drugs often clear the infection and prevent complications. A 14- to 21-day course of antibiotics is usually recommended, but some studies suggest that courses lasting 10 to 14 days are equally effective. In some cases, longer treatment has been linked to serious complications.

Intravenous antibiotics
If the disease has progressed, your doctor may recommend treatment with an intravenous antibiotic for 14 to 28 days. This is effective in eliminating infection, although it may take some time to recover symptomatically. Intravenous antibiotics can cause various side effects, including a lower white blood cell count, gallstones and mild to severe diarrhea.

Avoid bismacine
The Food and Drug Administration (FDA) warns consumers and health care providers to avoid bismacine, an injectable compound prescribed by some alternative medicine practitioners to treat Lyme disease. Bismacine, also known as chromacine, contains high levels of the metal bismuth. Although bismuth is safely used in some oral medications for stomach ulcers, it's not approved for use in injectable form or as a treatment for Lyme disease. Bismacine can cause bismuth poisoning, which may lead to heart and kidney failure.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.

You can decrease your risk of getting Lyme disease with some simple precautions:

• Wear long pants and sleeves. When walking in wooded or grassy areas, wear shoes, long pants tucked into your socks, a long-sleeved shirt, a hat and gloves. Try to stick to trails and avoid walking through low bushes and long grass. Keep your dog on a leash.
• Use insect repellents. Apply an insect repellent with a 10 percent to 30 percent concentration of DEET to your skin and clothing. Choose the concentration based on the hours of protection you need — the higher the concentration of DEET, the longer you are protected. A 10 percent concentration protects you for about two hours. Keep in mind that chemical repellents can be toxic, and use only the amount needed for the time you'll be outdoors. Don't use DEET on the hands of young children or on infants younger than age 2 months. According to the Centers for Disease Control and Prevention, oil of lemon eucalyptus, a more natural product, offers the same protection as DEET when used in similar concentrations. Don't use this product on children younger than 3 years.
• Do your best to tick-proof your yard. Clear brush and leaves where ticks live. Keep woodpiles in sunny areas.
• Check yourself, your children and your pets for ticks. Be especially vigilant after spending time in wooded or grassy areas. Deer ticks are often no bigger than the head of a pin, so you may not discover them unless you search carefully. It's helpful to shower as soon as you come indoors. Ticks often remain on your skin for hours before attaching themselves. Showering and using a washcloth may be enough to remove any unattached ticks.
• Don't assume you're immune. Even if you've had Lyme disease before, you can get it again.
• Remove a tick with tweezers. Gently grasp the tick near its head or mouth. Don't squeeze or crush the tick, but pull carefully and steadily. Once you've removed the entire tick, dispose of it and apply antiseptic to the bite area.

©1998-2009 Mayo Foundation for Medical Education and Research (MFMER). Terms of use.