“Doc, what’s this scaly rash on my arm? Do I have ringworm again?” A lot of the rashes I see in my dermatology clinic are red and scaly. In fact, what first drew me to dermatology as a profession was watching a dermatologist distinguish between seemingly similar red, scaly rashes all day. It intrigued me at the time, and I wanted to be just like her. 

I can always tell when my patient is a farmer, because they usually treat any rash as ringworm before coming to see me. How does ringworm happen and why are farmers so familiar with it? Ringworm, first of all, is not a worm. It is actually caused by a fungus that infects our skin and causes a circular rash wherever the fungus came in contact with our skin. Without treatment, the circle will continue to expand and enlarge, forming concentric rings. The rash usually itches and is bothersome. 

There are several families of fungus that can cause ringworm (tinea corporis in medical speak). They can be spread directly from other people, animals, or soil. The most severe infections typically happen when we get ringworm from animals. Growing up on a farm, I am very familiar with how much farmers interact with their livestock and pets. Farmers are accustomed to diagnosing ringworm on their animals and often will treat themselves if they see a similar rash. I’m pretty sure every farm family has had at least one member who has come down with this common infection at one time.

But all that is scaly, and circular is not ringworm. I remind my patients, especially farmers, that there are lots of different rashes that can look similar. It is not always in your best interest to try to self-diagnose and treat. 

Nummular eczema is a type of eczema that forms red, scaly, circular patches on our skin. Granuloma annulare is another rash that forms raised rings on the skin. These are both treated differently than fungal infections and make up the most common rashes that are misdiagnosed as ringworm. 

There are other, less common, rashes that can signify underlying medical conditions inside your body. Even though ringworm is a common, non-dangerous skin infection, if your rash doesn’t improve with over-the-counter antifungals you should always check with your doctor. 

Richard P. Holm, MD, passed away in March 2020 after a battle with pancreatic cancer. He is founder of The Prairie Doc. For free and easy access to the entire Prairie Doc library, visitwww.prairiedoc.org and follow Prairie Doc on Facebook. Mandi Greenway, M.D. is a contributing Prairie Doc® columnist. She practices dermatology in Mitchell, S.D.