The Bull’s-Eye Rash and Beyond: Identifying Lyme’s Early Signs

Every June, after the first warm weekend of yard work and trailhead parking lots, the same conversation starts up at kitchen tables across Maine. Someone pulled a tick off a kid’s hairline. A neighbor found a red mark on the back of their knee. Nobody is quite sure what they are looking at. And that uncertainty matters here more than almost anywhere else in the country.

Why this rash matters more in Maine and New Hampshire

Maine reported 3,035 Lyme disease cases in 2024 (preliminary, through December 3), a new state record up from 2,943 the year before. In 2023, Maine’s incidence rate of roughly 213 cases per 100,000 ranked among the three highest in the nation, alongside Rhode Island and Vermont. New Hampshire sits in the same tier. The CDC counts it as a high-incidence Lyme state, with a recent surveillance rate of about 63 cases per 100,000, and NH’s health department lists Lyme as one of its most commonly reported tickborne diseases.

The map is also widening. The Maine CDC notes that cases climb each year as the deer tick spreads throughout the state, no longer confined to the southern counties but reaching midcoast and Down East communities that did not used to worry much about it. So the early Lyme rash, called erythema migrans, is now something far more Mainers need to recognize on sight. For the full regional picture, our complete Maine and New Hampshire tick and Lyme guide covers prevention, removal, and testing in one place.

What erythema migrans actually is

Erythema migrans is the skin reaction that shows up at the site of an infected tick bite as Lyme bacteria spread outward through the tissue. It is the single most useful early clue we have. The CDC reports that the rash occurs in over 70 percent of people who develop Lyme disease, which makes it more common than any blood marker you could check in the first week.

That last point is worth sitting with. The rash is not a side note to Lyme. For most people, it is the first and clearest signal the body gives.

The myth of the perfect bull’s-eye

Here is what surprises people. The textbook bull’s-eye, a red ring with a clear center inside another ring, is actually uncommon. A 2022 study published in PMC looked at erythema migrans lesions and found that only 2 of 35 (about 6 percent) showed the classic ring-within-a-ring pattern. The most frequent appearance, in 51 percent of cases, was a solid, uniform patch. Most lesions were pink (74 percent), oval rather than perfectly round (63 percent), and had well-defined edges (92 percent). The authors put it plainly: public education should deemphasize the bull’s-eye form and stress how variable the rash really is.

If you have been waiting to see a crisp target before you worry, you are using the wrong picture. A flat, expanding, evenly colored oval is the version most people actually get.

Timing, size, and how it feels

The rash usually appears 3 to 30 days after an infected bite, with an average onset of about a week, a window the Maine CDC and the federal CDC both cite. It starts small and expands gradually over several days. Left alone, it can reach 12 inches (about 30 cm) across or more. That slow, steady growth is one of its signatures. A spider bite or skin irritation tends to flare and then fade within a day or two. Erythema migrans keeps creeping outward, often a little wider each morning than it was the night before.

How it feels is another useful tell. The CDC describes the rash as warm to the touch but rarely itchy or painful. That is close to backwards from what most people expect. We are trained to read an itchy, angry red mark as the dangerous one. With Lyme, the quiet patch that barely registers is often the one that counts.

Atypical rashes that fool people

The trouble is that erythema migrans does not always behave. The CDC’s own image gallery documents lesions that are bluish in hue with no central clearing, red-blue with partial clearing, and patches with dusky or crusted centers. They can appear on the chest, the back, the trunk, behind a knee, anywhere a tick managed to attach. Skin tone changes the picture too, and on darker skin the rash can look more like a bruise than a ring.

And sometimes there is no rash at all, or it comes with company. Early Lyme often arrives with flu-like symptoms, alongside the rash or instead of it. MedlinePlus, the NIH consumer health service, lists fever and chills, a general ill feeling, headache, joint pain, muscle aches, and a stiff neck among early symptoms that begin days to weeks after infection. The CDC notes those same flu-like signs can show up with no rash present. A summer fever with body aches and no obvious cause deserves a second thought in tick country.

Why you should not wait for a blood test

This is the part that trips up careful people. The standard Lyme blood test looks for antibodies, and antibodies take time to build. CDC clinical guidance is direct: serologic tests can be falsely negative during the first few weeks of infection, exactly when erythema migrans is most common. The same guidance says patients with a likely rash and possible tick exposure in an endemic area should be treated promptly, regardless of whether early testing is ordered.

In other words, a negative test in week one does not clear you, and a clear rash plus a plausible bite in a place like Maine is enough to act on by itself. If you want to understand the reasoning behind that, our piece on how accurate Lyme testing is walks through the two-tier system and its early-window blind spot.

There is real reward for moving early. MedlinePlus notes that an untreated rash can last four weeks or longer, while the CDC reports that people treated with appropriate antibiotics in the early stages usually recover rapidly and completely. Early recognition is the whole game.

When to act and what to do

So what does a reasonable person do with all this? Check your skin after time outdoors, and check the spots ticks like: the scalp, behind the ears and knees, the waistband, the armpits. If you find an expanding patch, especially one that is warm but not itchy and keeps growing day over day, photograph it with a coin or ruler beside it for scale and contact a healthcare provider. If you ran a summer fever with aches and a stiff neck after being in the woods or your own brushy backyard, mention the tick exposure even if you never saw a bite or a rash.

Most Mainers and New Hampshire residents who catch Lyme early do well. The harder cases tend to be the ones that went unrecognized for weeks. A small share of people report symptoms that linger after treatment, a topic we cover in our look at post-treatment Lyme disease and what the research shows. The best defense against any of that is knowing what the rash really looks like, which, for most people, is nothing like a target at all.

Sources

• U.S. Centers for Disease Control and Prevention. Lyme Disease Rashes. 2024. https://www.cdc.gov/lyme/signs-symptoms/lyme-disease-rashes.html
• U.S. Centers for Disease Control and Prevention. Signs and Symptoms of Untreated Lyme Disease. 2024. https://www.cdc.gov/lyme/signs-symptoms/index.html
• U.S. Centers for Disease Control and Prevention. Clinical Treatment of Erythema Migrans Rash. 2024. https://www.cdc.gov/lyme/hcp/clinical-care/erythema-migrans-rash.html
• U.S. Centers for Disease Control and Prevention. Lyme Disease Surveillance Data. 2024. https://www.cdc.gov/lyme/data-research/facts-stats/surveillance-data-1.html
• The Spectrum of Erythema Migrans in Early Lyme Disease: Can We Improve Its Recognition? PMC / peer-reviewed journal. 2022. https://pmc.ncbi.nlm.nih.gov/articles/PMC9687974/
• MedlinePlus, U.S. National Library of Medicine (NIH). Lyme disease. 2024. https://medlineplus.gov/ency/article/001319.htm
• Maine Center for Disease Control & Prevention. Lyme Disease. 2025. https://www.maine.gov/dhhs/mecdc/diseases-conditions/insect-borne-diseases/ticks/lyme
• Maine Center for Disease Control & Prevention (Maine Tracking Network). Tickborne Diseases (annual Lyme, anaplasmosis, and babesiosis case counts). 2025. https://data.mainepublichealth.gov/tracking/tickborne
• New Hampshire Department of Health and Human Services. Tickborne Diseases. 2024. https://www.dhhs.nh.gov/programs-services/disease-prevention/infectious-disease-control/tickborne-diseases
• Outbreak News Today. Maine reports more than 3,000 Lyme disease cases in 2024. 2024. https://outbreaknewstoday.substack.com/p/maine-reports-more-than-3000-lyme
• Portland Press Herald. Lyme cases set another record in Maine as ticks expand in midcoast and Down East. 2024. https://www.pressherald.com/2024/12/09/lyme-cases-set-another-record-in-maine-as-ticks-expand-in-midcoast-and-down-east/

This article is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare provider before making any health decisions.