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Lyme disease, or borreliosis, is a potentially serious illness that can develop when bacteria pass from black-legged ticks to humans.

Lyme disease is the most common tick-borne infectious disease in the United States. The ticks pick up Borrelia burgdorferi bacteria from mice and deer and pass the bacteria to humans through their bites.

At first, a rash may appear, and it may fade away without treatment. In time, Lyme disease complications can affect the joints, heart, and nervous system.

The Centers for Disease Control and Prevention (CDC) registered 23,558 confirmed cases of Lyme disease in 2018. The highest rate was in Pennsylvania.

An erythema migrans (EM) rash should be reported to a doctor, as it may indicate Lyme disease.Share on Pinterest
A Lyme disease rash. Image credit: HeikeKampe/ istock

The early symptoms of Lyme disease are usually very mild. Some people may not have any, or they may mistake these symptoms for the flu.

Stage 1: Early Lyme disease

Erythema migrans is a rash that often appears in the early stage, 3–30 days after the infection develops.

The rash develops in 70–80% of people with Lyme disease, and it:

  • typically begins as a small red area that expands over several days
  • ultimately reaches a diameter of 12 inches, or about 30 centimeters
  • may lose its color in the center, giving it a bull’s-eye appearance
  • usually starts at the site of the tick bite, though it can appear elsewhere as the bacteria spread
  • is not painful or itchy but may be warm to the touch

Depending on the tone of a person’s skin, the rash may not be very noticeable, or it may not show.

Stage 2: Later symptoms

Other symptoms can take months to emerge after the tick bite. They include:

  • headaches
  • neck stiffness
  • additional rashes
  • facial palsy — a loss of muscle tone in one or both sides of the face
  • arthritis and swelling in the joints
  • muscle, tendon, and bone pain
  • nerve pain
  • shooting pains, numbness or tingling in the hands or feet
  • heart palpitations

These symptoms may go away without treatment within a few weeks or months. However, some people develop chronic Lyme disease and have lasting symptoms.

Around 60% of people who do not receive treatment for the disease develop recurrent episodes of arthritis with severe swelling, especially in the large joints.

Post-treatment Lyme disease syndrome

Some people who have received care for the disease still experience post-treatment Lyme disease syndrome, which some refer to as chronic Lyme disease.

This involves nonspecific symptoms, such as fatigue and joint pain, that can persist for months after treatment.

Antibiotics are unlikely to help in this instance. Instead, the treatment aims to relieve the symptoms, which resolve in time. An approach may combine resting with anti-inflammatory medications.

In the U.S., the bacteria that cause Lyme disease enter the body through the bite of an infected black-legged tick.

The tick, either an adult or a nymph, bores a tiny hole in the skin and inserts its mouth into the opening, attaching itself to the host.

Ticks tend to latch onto hard-to-see areas, such as the scalp, armpits, and groin.

They usually need to be attached to the skin for at least 36–48 hours to pass on the bacteria. Larger adult ticks are easy to see, and most people can remove them relatively quickly. However, young ticks are barely visible and may remain unnoticed.

Is person-to-person transmission possible?

No. Lyme disease cannot spread:

  • between humans
  • from pets to humans
  • through air, food, or water

Lice, mosquitoes, fleas, and flies also do not transmit it.

Pregnancy and breastfeeding

Some small studies have linked Lyme disease during pregnancy to developmental differences or fetal death. Confirming this will require further research.

There have been no reports of transmission through breastfeeding. However, a doctor may recommend stopping breastfeeding while receiving treatment.

During pregnancy, people need a different type of antibiotic to treat Lyme disease.

Anyone with a rash that may have occurred with exposure to a tick should receive medical attention at once.

Be ready to describe the possible exposure. This might involve, for example, a recent hike in an area where ticks are common.

If a person removes a tick, they should take a photo of it and research the type.

It is worth highlighting that anyone who does not receive early treatment for Lyme disease may go on to experience more severe symptoms. These can emerge years later.

If a person has been exposed to a tick in an area where Lyme disease is common, treatment can start even without a confirmation of Lyme disease.

This is called prophylactic treatment, and it can prevent Lyme disease from developing if the bacteria are present.

Treatment should begin as soon as possible, and it usually involves antibiotics. Most people who receive early treatment have a full, rapid recovery.

The best way to prevent Lyme disease is to avoid tick bites.

Here are some ways to do this:

  • Know where ticks are likely to be.
  • Use repellent on the skin, clothing, and hiking or camping gear.
  • Give pets anti-tick treatment.
  • Check all gear, clothes, and pets for ticks after being outdoors.
  • Shower after coming in from outside and check for ticks.
  • Dry clothes at high temperatures to kill ticks.
  • Ask a pest control service about how to keep ticks out of the yard.
  • Remove ticks quickly and correctly.
  • Be alert for the symptoms of Lyme disease.

Tick repellent is available for purchase online.

When searching the body for ticks, be sure to check:

  • under the arms and behind the knees
  • in and around the ears
  • in the belly button
  • in all areas of hair
  • between the legs
  • around the waist

Learn more about removing ticks here.

If a tick is attached to the skin for less than 24 hours, it is unlikely to transmit the bacteria that cause Lyme disease.

Lyme disease can develop if a black-legged tick passes on B. burgdorferi bacteria through a bite.

Early on, a person may develop a rash with a ring or bull’s-eye shape. Treatment with antibiotics is usually effective.

Complications such as joint pain can arise later and may require a different approach.