The most recognizable sign of Lyme disease is a distinctive expanding rash that appears at the site of a tick bite, typically between 3 and 30 days after the bite occurs. More than 70% of people with Lyme disease develop this rash. But not everyone does, and the rash doesn’t always look the way you’d expect, so knowing the full range of symptoms at each stage is important for catching the infection early.
The Rash: What It Actually Looks Like
The Lyme rash, called erythema migrans, is often described as a “bull’s-eye,” but that classic target pattern is only one of several forms it can take. It may appear as a solid red oval plaque, an expanding circle with central clearing, a bluish-hued patch without any clearing at all, or a lesion with a crusty center. Some people develop multiple rashes in different locations on the body, sometimes with dusky-colored centers. The key feature across all these variations is that the rash expands over days, growing outward from the bite site rather than staying the same size.
If you see a rash like this, that’s often enough for a doctor to diagnose Lyme disease without waiting for blood test results. But about 30% of people with Lyme never notice a rash, either because it doesn’t develop, appears in a hard-to-see location like the scalp or back, or looks too faint on darker skin tones.
Early Symptoms Beyond the Rash
In the first 3 to 30 days after a tick bite, Lyme disease often feels like a mild flu. You may develop fever, chills, headache, fatigue, muscle and joint aches, and swollen lymph nodes. These symptoms can occur with or without a rash, which is what makes early Lyme so easy to dismiss. Many people attribute the achiness and fatigue to a summer cold or simply being run down, especially if they never noticed a tick on their body.
What sets Lyme apart from a typical virus is the context: these symptoms appearing during or after time spent in areas where black-legged ticks are common, particularly between late spring and early fall. If you’ve been in wooded or grassy areas and develop unexplained flu-like symptoms, Lyme should be on your radar even if you didn’t see a tick or a rash.
Symptoms That Appear Weeks Later
If Lyme disease isn’t treated in the first few weeks, the bacteria can spread through the bloodstream and begin affecting multiple body systems. This second stage, called early disseminated Lyme, produces symptoms that can be harder to connect to a tick bite. Severe fatigue, intermittent muscle and joint pain, numbness in the arms and legs, vision changes, and cognitive difficulties like short-term memory problems and trouble multitasking are all common at this stage.
Two symptoms are particularly telling. Facial paralysis, where one side of the face droops (Bell’s palsy), is a well-known neurological sign of Lyme. Cardiac involvement can also occur, causing an abnormally slow heart rate, irregular palpitations, feeling faint, or unexpected difficulty with exercise. If you experience any of these, particularly facial drooping or sudden heart rhythm changes, mention any possible tick exposure to your doctor, even if it happened weeks earlier.
Late-Stage Lyme Disease
Without treatment, about 60% of people infected with Lyme develop arthritis. The knee is the most commonly affected joint, with recurrent episodes of swelling that can be significant. The wrists and ankles can also be involved, but the pattern of a swollen knee that flares and subsides is the hallmark of late Lyme arthritis. This can develop months after the initial infection.
Most cases of Lyme arthritis clear up with a course of oral antibiotics lasting about 30 days. For those who don’t respond to the first round, intravenous antibiotics usually work. However, roughly 10% of people with Lyme arthritis continue to have joint inflammation even after the bacteria are eliminated. Research from Harvard has shown this happens because fragments of the dead bacteria remain in the joint fluid and continue triggering an inflammatory response, even when the infection itself is gone.
How Lyme Disease Is Diagnosed
If your doctor suspects Lyme disease based on your symptoms and exposure history, they’ll order a blood test that looks for antibodies your immune system produces in response to the Lyme bacteria. The standard approach uses two-tier testing: a first-step screening test, and if that comes back positive or borderline, a second confirmatory test run on the same blood sample. If the first test is negative, no further testing is needed.
There’s an important timing limitation to be aware of. Your body needs several weeks to produce enough antibodies for the test to detect. During the first few weeks of infection, blood tests frequently come back falsely negative. Sensitivity improves significantly after 4 to 6 weeks have passed since infection. This is why doctors will often diagnose and treat early Lyme based on the rash alone, without waiting for blood work, since waiting for accurate test results could mean missing the window for the easiest treatment.
Assessing Your Tick Exposure Risk
Lyme disease is transmitted exclusively through the bite of infected black-legged ticks (also called deer ticks). These are smaller than the common dog tick and have a distinctive appearance: an orange-red body with a dark brown or black plate on their upper back. Dog ticks, by contrast, are larger with mottled brown and white markings and do not transmit Lyme.
One reassuring detail: an infected tick generally needs to be attached for more than 24 hours before it can transmit the Lyme bacteria. If you find and remove a tick the same day it attached, your risk is low. Ticks that are still flat and small haven’t been feeding long. Engorged ticks, visibly swollen with blood, have been attached longer and carry more transmission risk.
Not every tick carries Lyme, and not every bite from an infected tick leads to infection. But if you pulled off a tick that was clearly attached and feeding, especially a small black-legged tick, watch closely for symptoms over the next 30 days. A rash at the bite site, flu-like symptoms, or any of the neurological or cardiac signs described above warrants a call to your doctor. Early treatment with antibiotics is highly effective and prevents the more serious stages of the disease from developing.