Lyme disease is a bacterial infection spread through the bites of infected ticks. It is the most common tick-borne illness in the United States, with an estimated 476,000 people diagnosed and treated each year. When caught early, a short course of antibiotics clears the infection in most people. Left untreated, it can spread to the joints, heart, and nervous system.
What Causes Lyme Disease
Lyme disease is caused by a type of bacteria called Borrelia burgdorferi (and rarely, a related species called B. mayonii). These bacteria live inside certain ticks and enter your bloodstream when an infected tick bites you and stays attached long enough to feed.
In the northeastern, mid-Atlantic, and north-central United States, the blacklegged tick (also called the deer tick) is the carrier. Along the Pacific Coast, a close relative called the western blacklegged tick transmits the infection. Not every tick carries the bacteria, but in areas where Lyme disease is common, a significant percentage do. States like Maine, Massachusetts, Pennsylvania, and Wisconsin have especially high rates.
Early Symptoms: Days to Weeks After a Bite
The first signs of Lyme disease typically appear within days to about a month after a tick bite. The most well-known symptom is a spreading rash at the site of the bite, often described as a “bullseye” pattern with a red center, a clear ring, and a red outer ring. However, the classic bullseye pattern is actually uncommon. In one study, only about 9% of patients had the textbook bullseye shape. The rash more often appears as a solid red patch that gradually expands outward over several days. Some research suggests that nearly half of people with confirmed Lyme disease never develop a noticeable rash at all.
Along with the rash, early Lyme disease often feels like a mild flu. You may notice fever, fatigue, muscle aches, and joint pain that seems to move around your body, showing up in different spots on different days. Because these symptoms overlap with so many other illnesses, Lyme disease is easy to miss if you don’t recall being bitten or don’t see a rash.
What Happens When It Spreads
If the infection isn’t treated in its early stage, the bacteria can move beyond the bite site to other parts of the body within weeks to months. This stage, called early disseminated Lyme disease, can affect the heart, brain, and spinal cord. Symptoms become more varied and more serious:
- Additional rashes appearing on parts of the body far from the original bite, a strong indicator of Lyme disease.
- Facial weakness or drooping on one or both sides, sometimes with difficulty closing an eyelid.
- Severe headaches and neck stiffness caused by inflammation around the brain and spinal cord.
- Heart problems including palpitations, irregular heartbeat, dizziness, or fainting, caused by inflammation of the heart.
- Numbness and tingling in the arms and legs.
- Swollen lymph nodes anywhere on the body.
Months to years after the initial bite, untreated Lyme disease can enter a late stage. The hallmark at this point is arthritis, usually in one large joint like the knee, with pain, swelling, and warmth that may come and go. Neurological effects can also develop: difficulty concentrating, brain fog, memory problems, nerve pain that feels like tingling or burning in the hands and feet, mood changes, and disrupted sleep.
How Lyme Disease Is Diagnosed
Diagnosis relies on a combination of your symptoms, exposure history, and blood tests. If you have the characteristic expanding rash and recently spent time in a tick-prone area, a doctor can often diagnose Lyme disease on sight and start treatment without waiting for lab results.
When blood tests are needed, the standard approach uses two steps performed on a single blood sample. The first test screens for antibodies your immune system produces in response to the bacteria. If that test comes back positive or borderline, a second, more specific test confirms the result. Both tests need to be positive for an official diagnosis. One important limitation: antibodies take time to develop, so testing too early (within the first couple of weeks after infection) can produce a false negative even when you’re infected.
Treatment and Recovery
Lyme disease caught in the early stage is treated with oral antibiotics, typically for 10 to 14 days. Most people recover completely with this short course. When the infection has spread to the nervous system or heart, treatment may need to be longer or more intensive, but the large majority of patients still make a full recovery.
For a subset of people, symptoms like fatigue, body aches, and difficulty thinking persist even after completing treatment. This is known as Post-Treatment Lyme Disease Syndrome, and its cause remains unclear. The lingering symptoms can last weeks to months. There is currently no proven benefit to extended antibiotic courses for this condition, and the standard recommendation is supportive care while symptoms gradually improve.
How to Remove a Tick Safely
If you find a tick attached to your skin, remove it immediately. Don’t wait for a doctor’s appointment. Use clean, fine-tipped tweezers to grasp the tick as close to your skin as possible, then pull straight up with steady, even pressure. Don’t twist or jerk, which can break off the mouthparts. If they do break off, your skin will push them out naturally over time, or you can try to pull them out with tweezers.
After removal, clean the bite area and your hands with soap and water or rubbing alcohol. Dispose of the tick by flushing it, sealing it in tape, placing it in a closed container, or dropping it in alcohol. Never crush a tick with your bare fingers. And don’t try home remedies like petroleum jelly, nail polish, or a hot match to make the tick detach. These methods can agitate the tick and potentially force infected fluid into your skin.
Reducing Your Risk
Lyme disease is most common in wooded and grassy areas where deer ticks thrive, especially during warmer months when ticks are most active. When spending time outdoors in tick-prone regions, wearing long pants tucked into socks and treating clothing with permethrin-based repellents reduces your exposure. Using insect repellent on exposed skin adds another layer of protection.
The single most effective habit is doing a thorough tick check after spending time outside. Ticks favor warm, hidden spots: the scalp, behind the ears, armpits, groin, behind the knees, and around the waistband. Showering within two hours of coming indoors helps wash off ticks that haven’t yet attached. The sooner you find and remove a tick, the lower the chance of infection, since the bacteria need time to transfer from the tick into your bloodstream.