What to Know About Erythema Migrans

Written by Kendall K. Morgan
Medically Reviewed by Zilpah Sheikh, MD on May 20, 2025
7 min read

It's a rash that's often the first symptom of Lyme disease. It's typically a circular red area. It might clear in the middle, forming a bull's-eye pattern, but most of the time it doesn't. It can spread up to 12 inches across and may be warm to the touch. It's not usually itchy or painful. It may appear in more than one place on your body.

The CDC estimates more than 475,000 people in the U.S. are diagnosed with Lyme disease each year. It's possible some of them don't have Lyme disease, but many cases may be missed.

About 70%-80% of people with Lyme disease (which is spread by ticks) have erythema migrans. It usually shows up at the site of a tick bite 3-30 days after you're bitten. It gradually expands, but it doesn't always appear the same on everyone.

Recognizing erythema migrans is important for early diagnosis and treatment of Lyme disease. But it's possible you could have the rash and not even know it, says John Aucott, MD, an infectious diseases physician at Johns Hopkins Medicine in Baltimore, MD.

"Some people probably have it, but don't see it, because if you live alone, and it's in the middle of your back or behind your knee, you don't really look at those areas usually in the mirror," Aucott says. "The lesions themselves aren't super painful or super itchy. They can be minimally, but not in the way that you would definitely notice it."

Erythema migrans may also be harder for you to spot depending on your skin color. "Darkly pigmented skin can make it more difficult to see the lesion," Aucott says.

As a result, his study showed Black people are more likely to find out they have Lyme disease at a later, more advanced stage. It can also take longer to get antibiotic treatment, suggesting a need for more awareness among doctors and the public to reduce racial differences in Lyme disease treatment and outcomes.

Erythema migrans is often the first sign of being infected with the bacteria Borrelia burgdorferi, which causes Lyme disease. Infected deer ticks can transmit the bacteria if they bite you and latch on. Dog ticks and wood ticks don't transmit Lyme disease. But it's your immune system's response to the bacteria that causes your rash.

"We don't like bacteria multiplying in our tissue, so our immune system responds to that, and the immune cells go in to fight the bacteria, and in the process of fighting it, they elaborate different inflammatory mediators — cytokines and chemokines — that cause the immune system to react in a good way," Aucott says.

"Part of that is vasodilation of blood vessels that brings in more blood flow. That causes redness and warmth and inflammatory cells that again elicit inflammatory mediators that cause fever and all those good things. So, all the symptoms really are from your immune response to the bacteria. The bacteria per se doesn't cause it."

The first sign of erythema migrans is redness at the site of the tick bite. It expands into a round or oval red skin lesion. Most commonly, it's a round or oval rash that expands to more than 2 inches in diameter. Sometimes, the inside of the lesion clears, leaving a bull's-eye pattern. 

Because erythema migrans is an early symptom of Lyme disease, you may also have symptoms of an infection, including:

Many cases of Lyme disease are misdiagnosed at first. Early symptoms are common ones that happen with many illnesses. Although not all people with Lyme disease have erythema migrans, recognizing when it's present can be key in early diagnosis and treatment.

"Borrelia is not a respiratory bacteria, so it does not cause runny nose, cough, and pulmonary symptoms like flu or COVID does," Aucott says. "But all infections cause fever, malaise, chills, and achiness. During [the COVID-19 pandemic], we were getting people who got told they had COVID when they had Lyme disease."

When erythema migrans is present, it can be the basis of a Lyme disease diagnosis by itself, since early blood tests aren't always reliable.

"Only about 20% or 30% of the lesions have that classic ring within a ring," Aucott says. "It is always round or oval. It's almost never the classic target lesion, so we see misdiagnosis by patients and physicians all the time."

When in doubt, it's best to assume that a circular or oval, red rash is a sign of Lyme disease and get it checked out, especially during warmer months in a place where Lyme disease is prevalent, Aucott advises.

"I have this saying that there's no such thing as a spider bite during May, June, or July in Maryland, because people say, 'Oh, it's a spider bite. It wasn't a target lesion,'" he says. "If it's an endemic area during the high-season months, the pretest probability of a round, red lesion being Lyme disease is extraordinarily high."

The lesion expands over several days to a month. Sometimes, you may get multiple circular or oval shapes as the bacteria spreads. It may have blisters in the center, but that's not common. 

Over time, the rash fades, even if your Lyme disease doesn't go away. Aucott recommends taking a picture of your rash to show your doctor in case it takes time to get in to see them.

Because Lyme disease is caused by bacteria, it's treated with antibiotics. The sooner you start taking them, the quicker and more complete your recovery will be.

Oral antibiotics. Early-stage Lyme disease is treated with antibiotics you take by mouth. Doxycycline is usually used to treat Lyme disease in adults and children over 8. Amoxicillin or cefuroxime is often used for younger children and pregnant or breastfeeding women. Oral antibiotics are usually given for 14-21 days, although a 10- to 14-day course may be as effective. 

Intravenous (IV) antibiotics. If your Lyme disease involves your central nervous system, you may need IV antibiotics for 14-28 days. This will get rid of your infection. But it may take a while for you to completely get better.

If no rash is present or it goes unnoticed, and you don't remember being bitten by a tick, it can be hard to diagnose Lyme disease. Testing early in the disease process may show a false negative. That's because your body hasn't had time to make an immune response that can be measured. Once your body develops a response, you may get a positive test for years, even after your Lyme disease has been properly treated.

"Even without antibiotics, the rash goes away," Aucott says. "The problem is that, during that period in more than half the people, the bacteria spreads into the circulation or lymphatics to other areas of the body. So, if you don't treat during the rash phase, then people have what's called secondary Lyme, which can involve the nervous system, the heart, even 6-12 months later. Lyme arthritis represents those bacteria that left the skin [and entered the joints], but the arthritis doesn't usually show up for even six months to a year later."

Deer ticks that carry the bacteria causing Lyme disease are most prevalent in New England, the mid-Atlantic states, and the upper Midwest of the U.S. They live in moist and woody environments. If you're going to be in an area like this, use an insect repellent that contains DEET, picaridin, IR3535, oil of lemon eucalyptus, para-menthane-diol, or 2-undecanone.

You should also:

  • Check your body for ticks after being outside.
  • Check your clothing and pets for ticks.
  • Place your clothes in a dryer on high heat to kill ticks.
  • Remove attached ticks with tweezers as soon as you notice them.
  • Watch for symptoms of Lyme disease after you remove a tick.
  • Contact your doctor if you get a fever or rash, even if you don't remember being bitten. 
  • Treat your animals using veterinarian-prescribed tick prevention products to keep them from bringing ticks into your house. 
  • Discourage deer from coming into your yard by removing plants that attract them and putting up fences. 
  • Create a tick-safe zone in your yard by using chemical control agents and keeping the area clean of yard debris.

Erythema migrans is a circular or oval, red rash that often forms when your immune system reacts to the infection from the bacteria causing Lyme disease. In about 20% of cases, the rash is a bull's-eye pattern. You get it after a tick bite, and usually it doesn't itch or hurt. If you have a rash and think it might be erythema migrans, see your doctor to find out. You'll need antibiotics to clear the infection.

How soon does the rash appear after a tick bite?

Not everyone bitten by a tick gets erythema migrans or Lyme disease. If you do get this rash, it'll show up 3-30 days after you're bitten.

Can erythema migrans go away without treatment?

Yes. It usually will go away without treatment. But you can still have the infection in other parts of your body, which can cause serious health issues. It's important to see your doctor if you have a rash now or have had one recently, as it could be erythema migrans.

How is erythema multiforme different from erythema migrans?

Erythema multiforme is a skin condition caused by allergic reactions to medicine or an infection. It's often caused by the herpes simplex virus. This rash may have red, raised spots all over your body. They might look like targets with purple or grey centers.

Is erythema migrans painful or itchy?

No, unlike many other rashes. That's one reason you can have it and not notice, depending on where it is on your body. But you may have other symptoms of an infection, such as body aches, fever, or fatigue.