Bullseye Rashes: Ringworm and Lyme Disease Differences
A Picture Guide Comparing Rashes Caused by Ringworm and by Lyme Disease
When a mystery "bullseye" rash suddenly appears—a red circle on your skin—it’s often hard to tell whether it is caused by Lyme disease or ringworm. Decisions can be even more complicated if you do not remember being bitten by a tick. When I had my first bullseye rash, I knew Lyme was a possibility, but I did not know what else could cause it. In my research, I found only two conditions that cause that distinct circular rash: Lyme disease and ringworm.
There are many similarities between these ring-shaped rashes, which makes it harder to distinguish them, but there are differences. I will briefly cover some information about each disease, and I have also included a picture reference guide to help you identify which rash you may have.
Ringworm or tinea is a common skin disorder. The most common form of ringworm affects the body and is medically known as tinea corporis. This skin disorder is called “ringworm” because of an early, mistaken belief that it was caused by a parasite or worm. The condition is actually the result of a fungus (a "dermatophyte") that consumes dead skin and other dead cells on the surface of the body.
When fungus affects the skin, it often produces the round spots of classic ringworm. The ringworm rash generally has the following characteristics when found on most of the body, though it may look different in other places like the foot or the scalp:
- One or more reddish, inflamed, scaly or crusty, raised rings, from one to a few centimeters in diameter.
- At first, the lesions caused by ringworm appear like spots or dots, later on taking a circular shape. The circle is created when the central parts of the lesions begin to heal, while the edges continue to expand, covering up larger areas of skin.
- The rings have an "active" outer border as they slowly grow and advance.
- The lesions may have either a dry or moist texture. Dry lesions are commonly associated with inflammation and scaling of the skin, while moist lesions are commonly associated with small blisters along the edges of the rings and the formation of a crust.
- Lesions may be itchy and tender, although the intensity of these symptoms is usually mild or moderate. These skin sensations are generally the only symptoms that will appear.
Doctor-prescribed antifungal medications should be able to stop the proliferation of the fungi within the first few days of treatment, and completely clear up the infection within two or three weeks. If left untreated, the infection may go away after about a month.
Here is more information on ringworm from the National Institutes of Health.
Lyme disease is an infection caused by Borrelia burgdorferi, a bacterium called a spirochete that is carried by deer ticks. An infected tick can transmit the spirochete to the humans and animals it bites. Untreated, the bacterium travels through the bloodstream, establishes itself in various body tissues, and can cause a number of symptoms, some severe.
The first symptom is usually, not always, a circular rash called erythema migrans, or EM rash, although some people with Lyme disease never see a rash. An EM rash generally has the following characteristics:
- It most often appears as a central spot, surrounded by a ring of clear skin, which is surrounded in turn by an expanding red rash, forming the appearance of a bullseye. Occasionally the rash is a solid red blotch with a lighter center. The red patches vary in how light or dark they may be.
- It is not usually painful or itchy. The rash is level with the skin and is not scaly or crusty. But please note that if other organisms besides the spirochete infect a tick bite (co-infection) they may cause an itchy or painful rash.
- The rash usually (but not always) radiates from the site of the tick bite. You can be bitten on the neck and have your rash appear on your leg. The rash can occur anywhere on the body, most commonly on the legs, neck, arms and back.
- The rash appears for an average of one to two weeks, but may be seen at any time between two and 30 days after disease transmission.
- The EM rash will not react to any fungal or hydrocortisone creams.
- The rash has an average diameter of four to six inches, but may range from one inch to two feet across.
- Symptoms elsewhere in the body can appear at the same time, including joint and muscle pain, fatigue, headaches, and cognitive difficulty. Many other symptoms will arise as the disease progresses.
If you suspect you may have Lyme disease, do not hesitate to go to a doctor’s office. This guide is not meant to replace your doctor’s care, but to help you educate yourself. And it’s wise to educate yourself, because many doctors, even infectious disease specialists, are not well informed about the dangers of Lyme disease. It is more widespread than many people think, not easy to diagnose, and not easy to treat, especially if it is not treated in the first few weeks. If misdiagnosed, Lyme disease can go on for months and years.
I personally have been battling this disease for two and a half years. I was misdiagnosed for eight months, even though I had the EM rash and my doctor saw it firsthand. Testing for Lyme disease is inaccurate and fails over 50% of the time. Fortunately, there are many resources available out there for research, and many doctors are becoming “Lyme-literate.”
Need more information? Here are a few places to start!