Lyme disease typically starts with flu-like symptoms and, in over 70% of cases, a spreading skin rash that appears 3 to 30 days after a tick bite. From there, untreated Lyme can progress through stages that affect the joints, nervous system, and heart. With roughly 476,000 people diagnosed and treated for Lyme disease each year in the United States, recognizing these symptoms early makes a real difference in outcomes.
The Rash: Not Always a Bullseye
The Lyme rash, called erythema migrans, is the most recognizable early sign. It shows up at the site of the tick bite and gradually expands over days or weeks. Most people picture a neat bullseye pattern, but the rash actually takes several forms. It can appear as a solid red or bluish oval, a red-blue lesion with only partial clearing in the center, or multiple expanding patches with dusky centers. Some rashes have no central clearing at all. On darker skin tones, the rash may look more bruise-like than red.
The rash is typically not itchy or painful, which means it’s easy to overlook, especially if it appears on your back, scalp, or another spot you can’t easily see. And about 30% of people with confirmed Lyme disease never develop a rash, so waiting for one before seeking care can mean a missed diagnosis.
Early Flu-Like Symptoms
Within the same 3-to-30-day window after a tick bite, you may develop symptoms that feel a lot like the flu: fever, chills, headache, fatigue, muscle aches, joint pain, and swollen lymph nodes. These can occur with or without a rash. Because these symptoms overlap with so many common illnesses, they’re easy to dismiss, especially in the summer months when people attribute fatigue and body aches to heat or physical activity. The key distinguishing factor is context. If you’ve been in a tick-prone area and develop these symptoms, that combination matters.
Neurological Symptoms
If Lyme disease goes untreated in its earliest phase, the bacteria can spread through the bloodstream and begin affecting the nervous system. This stage, called early disseminated Lyme, typically develops weeks to months after the initial bite. The neurological symptoms can be striking.
Facial palsy (a sudden drooping or weakness on one or both sides of the face) is one of the more distinctive signs. About 9 out of every 100 Lyme cases reported to the CDC involve facial palsy. When peripheral nerves are affected, you may experience numbness, tingling, shooting pain, or weakness in the arms or legs. This is called radiculoneuropathy, and it shows up in roughly 4% of reported cases.
Lyme can also cause meningitis, an inflammation of the membranes surrounding the brain and spinal cord. That brings severe headache, fever, a stiff neck, and sensitivity to light. About 3% of reported cases involve meningitis or encephalitis.
Heart Symptoms
Lyme carditis occurs when the bacteria reach the heart tissue and interfere with the electrical signals that control your heartbeat. Symptoms include heart palpitations, chest pain, lightheadedness, fainting, shortness of breath, and difficulty breathing during physical exertion. Lyme carditis is less common than the neurological complications, but it can be serious. If you’ve been diagnosed with or suspect Lyme disease and develop any cardiac symptoms, that needs immediate medical attention.
Late-Stage Joint Swelling
Months after the initial infection, untreated Lyme disease most commonly settles into the joints. Lyme arthritis causes obvious swelling in one or a few joints, with the knees affected most often. Other large joints like the shoulder, ankle, elbow, jaw, wrist, and hip can also be involved. The affected joint may feel warm to the touch and hurt during movement.
One characteristic pattern that helps distinguish Lyme arthritis from other types: the swelling can come and go, or migrate from one joint to another. It may flare for weeks, resolve on its own, then return in the same or a different joint. In the shoulder, hip, or jaw, the swelling can be subtle enough that you notice the stiffness and pain before any visible changes.
Symptoms in Children
Children develop the same core symptoms as adults, including the rash, flu-like illness, and joint swelling. But a few things look different in kids. A child may develop multiple ring-shaped rashes on the body rather than a single expanding lesion. In later stages, children can develop trouble with speech, memory, and concentration. Because kids may not articulate these changes clearly, parents sometimes notice a shift in school performance or behavior before the child complains of specific symptoms.
Symptoms That Linger After Treatment
Some people continue to experience symptoms even after completing a full course of antibiotics. This is known as post-treatment Lyme disease syndrome. The hallmark symptoms are profound fatigue, widespread musculoskeletal pain, and cognitive problems, particularly difficulty with memory and word recall. Sleep disturbances, depression, tingling or unusual skin sensations, and radiating pain are also common. To qualify as post-treatment Lyme disease syndrome, symptoms must have started within six months of the original infection and persisted for at least six months after treatment.
The severity varies widely. Some people describe mild brain fog that gradually clears over months. Others deal with fatigue and pain significant enough to interfere with daily functioning. The condition remains an active area of medical debate, but the symptoms themselves are well documented and can be genuinely disabling for some patients.