Painful sores in or around the mouth are very common, but many people don’t know that they can have different causes. Two of the most frequent types are cold sores and canker sores. Although they may look similar at first, they are actually very different conditions.

Cold sores usually appear on or around the lips as small blisters that may form in clusters. They are caused by the herpes simplex virus type-1 (HSV-1) and are contagious. The virus can spread through close contact such as kissing or sharing items like utensils, glasses, or lip balm. Once someone is infected, the virus can remain inactive in the body and may reappear later due to triggers such as stress, illness, or too much sun exposure.

Common symptoms of cold sores include tingling or itching before the blister appears, painful blisters that eventually crust over, dry or irritated lips, and sometimes fever or swollen lymph nodes. Most cold sores heal on their own within two to three weeks, though antiviral treatments may help them heal faster.

Canker sores, on the other hand, appear only inside the mouth—on the tongue, cheeks, gums, or lips. They are small round ulcers that are usually white or yellow with a red border. Unlike cold sores, canker sores are not contagious and are not caused by a virus.

Their exact cause isn’t always clear, but they may be triggered by mouth irritation, accidental bites, certain foods, stress, or nutritional deficiencies. While painful, most canker sores heal naturally within one to two weeks. Over-the-counter treatments and simple remedies like saltwater rinses can help reduce discomfort.

In most cases, both types of sores are harmless and temporary. However, you should consider seeing a doctor or dentist if sores last longer than a few weeks, are unusually large or painful, keep returning frequently, or make it difficult to eat or drink.

Understanding the difference between these common mouth sores can help you manage them properly and know when it’s time to seek professional care.