Seeing a strange red ring on your child’s arm can be frightening, but most ring-shaped rashes are not medical emergencies. While it’s natural to worry, the first step is to stay calm and observe the rash closely. Take a photo, lightly mark the edge of the redness with a pen, and compare it several hours later to see if it’s spreading. If your child is otherwise acting normally, eating, playing, and doesn’t have a fever, it’s usually appropriate to contact your pediatrician rather than rush to the emergency room.

One possible cause is Lyme disease, especially if the rash is slowly expanding, isn’t very itchy or painful, and your child has recently been in wooded or grassy areas where ticks are common. Another common possibility is ringworm, a fungal infection that often has a raised, scaly border and is usually itchy. Insect bites, mild allergic reactions, contact dermatitis, and certain viral rashes can also create circular or ring-like marks that are generally easy to treat.

Seek emergency medical care right away if the rash is accompanied by difficulty breathing, swelling of the lips or face, a very high fever, severe pain, confusion, extreme sleepiness, a stiff neck, or a rapidly spreading purple or bruise-like rash. These symptoms may indicate a more serious condition that requires immediate attention.

If none of those warning signs are present, call your child’s pediatrician and describe when the rash appeared, whether it has grown, if it’s itchy or painful, and whether your child has recently been outdoors where ticks are common. Most ring-shaped rashes can be diagnosed and treated quickly, and with the right care, children usually make a full recovery.