Lyme Disease and Ticks
A bacterial infection spread by the bite of infected blacklegged (deer) ticks.
Last revised
Key takeaways
- Tick that spreads it: blacklegged (deer) tick
- Attachment usually needed to spread infection: 36 to 48 hours or more
- Most useful single change: Use an EPA-registered repellent with DEET, picaridin, IR3535, oil of lemon eucalyptus, PMD or 2-undecanone.
- Commonest mistake: Using nail polish, petroleum jelly or heat to make a tick detach.
- See a doctor if any of the signs under "When to get help" below apply to you.
Why it matters
Caught early it is usually treated with a short course of antibiotics, but missed infections can spread to the joints, heart and nervous system.
The numbers, in one place
| Measure | Figure |
|---|---|
| Tick that spreads it | blacklegged (deer) tick |
| Attachment usually needed to spread infection | 36 to 48 hours or more |
| Typical rash | an expanding red rash in about 70 to 80% of infections, 3 to 30 days after the bite |
| Highest-risk regions | the Northeast, mid-Atlantic and upper Midwest |
| Killing ticks on dry clothes | tumble dry on high heat for 10 minutes |
What helps
- Use an EPA-registered repellent with DEET, picaridin, IR3535, oil of lemon eucalyptus, PMD or 2-undecanone
- Treat boots, clothing and gear with 0.5% permethrin, or buy pre-treated clothing
- Shower soon after coming indoors and check your whole body, children and pets for ticks
- Remove an attached tick with fine-tipped tweezers, pulling upward with steady pressure, then clean the area
What to avoid
- Using nail polish, petroleum jelly or heat to make a tick detach
- Waiting for a bull's-eye rash; many rashes are solid red
- Applying permethrin directly to skin
In depth
Lyme disease is caused by Borrelia bacteria that live in the gut of infected ticks. When a tick feeds, the bacteria gradually move to its salivary glands and into the bite, which is why the tick usually has to stay attached for a long time before infection is likely. Most infections come from nymphs, young ticks about the size of a poppy seed, which are easy to miss.
After entering the skin, the bacteria spread outward, producing the expanding rash called erythema migrans. If untreated, they can travel through the bloodstream to other tissues. Weeks later, they can affect nerves, causing facial drooping, and the heart, causing Lyme carditis. Months later, some people develop arthritis, most often in the knees.
Ticks also carry other infections, including anaplasmosis, babesiosis and, in some regions, Powassan virus. Some ticks carry more than one. Doctors consider these when symptoms do not fit Lyme disease or do not improve with treatment.
Signs and symptoms
- An expanding red rash at or near the bite, often warm but not usually itchy or painful
- Fever, chills, headache, fatigue and muscle or joint aches
- Additional rashes on other parts of the body
- Facial palsy, a drooping on one or both sides of the face
- Heart palpitations, lightheadedness or shortness of breath
- Joint swelling and pain, often in a knee, coming weeks to months later
Causes and risk factors
- Spending time in wooded, brushy or grassy areas where ticks live
- Living in or visiting the Northeast, mid-Atlantic or upper Midwest
- Late spring and summer, when nymphs are most active
- Not using repellent or checking for ticks after outdoor activity
- Pets that bring ticks into the home
- Leaving a tick attached for more than a day
How it is checked
Early Lyme disease with a characteristic rash in someone who has been in a risk area is usually diagnosed by appearance, without a blood test. Blood tests often are negative in the first weeks, because antibodies take time to develop.
For later symptoms, doctors use a two-step blood antibody test, and may test joint fluid or spinal fluid in specific situations. Tests on the tick itself are not recommended to guide treatment. Positive results alone do not prove that current symptoms are from Lyme disease, so doctors interpret them with your history.
Related topics
- The Evidence on Antibiotics, Without the Hype (Immunity)
- What the Guidance Really Says About Malaria Prevention (Travel Health)
- What the Guidance Really Says About Athlete's Foot (Foot Health)
- Common Childhood Infections: What the Evidence Actually Says (Children's Health)
Where to go next
- Making Sense of Lyme Disease and Ticks
- Lyme Disease and Ticks: A Practical Checklist
- Infectious Diseases: The Complete Guide
- The Evidence on West Nile Virus and Mosquitoes, Without the Hype
- What the Guidance Really Says About Norovirus
When to get help
See your doctor if you develop a rash, fever, chills, headache, fatigue or joint aches in the weeks after a tick bite, and tell them where you have been. Call 911 for chest pain, fainting, a very slow or irregular heartbeat, or sudden weakness or drooping of the face.
Where this comes from
How this page was put together
Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.