Differences Between Ringworm and Other Skin Conditions

Despite its name, ringworm isn’t an infection caused by worms or a parasite. Rather, it’s an infection caused by fungi that can occur almost anywhere on your body, including your hands, feet, scalp, and groin. If you’ve ever had Athlete’s foot or jock itch, you’ve had an overgrowth of the exact same fungus that causes ringworm, known as “tinea.”

The typical ringworm rash resembles a flat, circular patch on the skin that grows increasingly larger. It gets its name from the red and raised ring that usually develops around the border of the rash. Sometimes, the ringworm rash is itchy and scaly, and as the rash grows, the skin in the middle may revert to your normal skin tone.

Many providers can diagnose ringworm just by looking at the rash. However, testing is sometimes necessary because several other types of skin conditions can mimic symptoms of ringworm.

Granuloma annulare is a chronic (long-term) skin condition that often has no symptoms other than a round rash with a red ring around the border—making its physical appearance extremely similar to ringworm. This condition often appears on the hands and feet, usually on both sides of the body, and may look dark red or yellow. 

Experts don’t know exactly what causes granuloma annulare, but it often develops after you’ve experienced a skin injury. Living with conditions like diabetes, HIV, and thyroid disease can also increase your risk of developing symptoms of granuloma annulare.

A dermatologist (a doctor who specializes in skin conditions) may be able to diagnose you with granuloma annulare just by looking at your skin and asking you questions, like if you’ve injured your skin lately or if you’re experiencing any itching or pain. They can also perform a biopsy by removing a small piece of the affected skin and sending it to a laboratory for a proper diagnosis.

Eczema is an umbrella term for many different types of inflammatory skin conditions. One type of eczema is nummular eczema, which causes round or “coin-shaped” patches on the skin, especially the arms, legs, hands, and torso. These patches can also be itchy and scaly, making it hard to tell the difference between nummular eczema and ringworm.

However, nummular eczema is usually more noticeably irritated and inflamed than a ringworm rash. The patches are more likely to ooze and crust over. Most dermatologists can diagnose nummular eczema just by looking at it, but if they aren’t sure, they can scrape away a small amount of skin and examine it more closely under a microscope.

An allergic reaction on the surface of the skin can result in contact dermatitis. This rash can be caused by several irritants or allergens, such as soap, makeup, certain fabrics or metals, poison ivy, and things you are personally allergic to.

Although contact dermatitis shares some characteristics with ringworm—like itchy and scaly patches—it doesn’t necessarily have a circular presentation. Contact dermatitis can be any shape or size. A contact dermatitis rash may also swell, blister, or become hot to the touch, which isn’t typical for ringworm.

It can be tricky to diagnose contact dermatitis on the spot unless you know you came into contact with an allergen and experienced a rash soon afterward. Instead, a dermatologist can diagnose contact dermatitis through a series of allergy tests to confirm what you’re allergic to.

Pityriasis rosea is a harmless skin rash without a clear cause, though experts theorize having a history of herpes can increase your risk of the condition. The first sign of pityriasis rosea is usually a round or oval scaly lesion with a raised border, known as a herald patch. Not everyone with pityriasis rosea gets a herald patch, but about 80% of people will see this lesion for up to two weeks before developing a larger-scale rash on their bodies.

The herald patch can look very similar to a ringworm rash, but it’s usually accompanied by other symptoms that make it easier for a provider to tell the difference between both conditions. Common symptoms of this condition include flu-like symptoms, a herald patch, and the development of numerous other skin lesions that can spread for up to two weeks. Generally, the patches go away on their own after eight weeks.

Lyme disease is a bacterial illness spread by infected ticks. About 70% to 80% of people with Lyme disease get a rash in the first several days or weeks after a tick bite. This rash often starts as a round, red patch and usually takes on a ringed appearance as it spreads. Think of it as resembling a bull’s eye. This is called an erythema migrans rash, and it can look similar to ringworm in this stage of the condition. 

However, not everyone gets an erythema migrans rash, and it’s not always circular or ringed. This is one way that a provider may be able to tell the difference between Lyme disease and ringworm. Lyme disease also commonly causes flu-like symptoms, like fever, headache, and muscle pain, while ringworm does not. 

If your provider is still unsure about your diagnosis, a blood test to detect the presence of antibodies to certain disease-causing bacteria may confirm that you have Lyme disease. These tests are more reliable the longer you’ve been infected, though, so your provider may also choose to test you for ringworm to make an accurate diagnosis.

Psoriasis is an inflammatory autoimmune condition that causes thick patches of raised, itchy, and scaly plaques to develop on the skin. There are several different kinds of psoriasis. While some don’t resemble ringworm, other types, like plaque psoriasis and inverse psoriasis, can have a round and red appearance that can sometimes be mistaken for ringworm. Like ringworm rashes, psoriasis patches are also often itchy. 

One of the most noticeable differences between ringworm and plaque psoriasis is that plaques are usually fully raised, while ringworm rashes are usually flat in the center. Ringworm also tends to be red and scaly, while plaques often have silvery scaling on top of red, inflamed skin. It may be more difficult to tell the difference between ringworm and inverse psoriasis, which causes red, smooth patches. 

To diagnose psoriasis, a healthcare provider will learn more about your medical history and perform a physical exam. If they’re unsure whether psoriasis is causing your rash, they may take a biopsy to rule out other causes and get a better look at the affected skin.

Seborrheic dermatitis is a non-contagious, inflammatory skin condition that causes an itchy and flaky rash, typically appearing on the scalp, face, and groin. However, some people develop a subtype of this condition known as petaloid seborrheic dermatitis, which causes a circular, ring-like rash. To understand whether your rash is due to seborrheic dermatitis or ringworm, your healthcare provider will visibly examine you and sometimes take a skin biopsy.

This condition is relatively common and most often occurs in people between the ages of 30 and 60. Excess oil production in your glands and triggers like stress and hormonal changes can increase your risk of developing symptoms. However, treatments like proper skincare and topical medications can keep symptoms at bay.

It’s sometimes hard to justify making an appointment with a healthcare provider when you “only” have a skin rash, but a rash that doesn’t go away after a day or two should be evaluated. Not only can a rash quickly spread to larger areas of the body or become uncomfortable, it can make you vulnerable to other skin infections and even be a sign of another underlying health condition.

See a healthcare provider as soon as possible if you have a rash that:

• Covers most of your body or spreads quickly
• Blisters or causes open sores on your skin
• Occurs alongside symptoms of an allergic reaction, like a swollen tongue or difficulty breathing
• Causes pain or a fever
• Keeps you awake at night
• Affects your eyes, lips, mouth, or genitals

You should also seek medical attention if you think your rash might be infected. Signs of an infected rash include redness, pain, swelling, warmth, pus or discharge, and foul odor.

Ringworm is a common fungal infection that causes a flat circular rash with a reddish ring around the border. Several other skin conditions can cause similar-looking rashes, like Lyme disease, pityriasis rosea, psoriasis, and nummular eczema.

Because each of these rashes requires a different treatment, a healthcare provider needs to make an accurate diagnosis before you start treatment.