Seeing a ring-shaped red rash on your child’s arm can be alarming, but many circular rashes are not medical emergencies. The first step is to stay calm and observe it carefully. Taking a photo and lightly marking the edge of the redness with a pen can help you determine whether the rash is expanding over the next several hours. If your child is otherwise feeling well, eating, playing, and does not have a fever, it is generally appropriate to contact your pediatrician for guidance rather than immediately going to the emergency room.

Several conditions can cause ring-shaped rashes. One possibility is Lyme disease, particularly if the rash is gradually expanding, is not especially itchy or painful, and your child has recently spent time in wooded or grassy areas where ticks are common. Ringworm, a common fungal infection, is another possibility and often appears as a circular rash with a raised, scaly border that may itch. Insect bites, mild allergic reactions, contact dermatitis, and certain viral infections can also produce circular skin changes.

Emergency medical care should be sought immediately if the rash is accompanied by symptoms such as difficulty breathing, swelling of the lips or face, a very high fever, severe pain, confusion, unusual drowsiness, a stiff neck, or a rapidly spreading purple or bruise-like rash. These signs may indicate a serious condition that requires urgent medical evaluation.

If none of these warning signs are present, contact your child’s pediatrician and be prepared to describe when the rash first appeared, whether it has changed in size, if it is itchy or painful, and whether your child has recently been in areas where ticks are common. Most ring-shaped rashes can be diagnosed and treated effectively, and with appropriate care, children typically recover well.