Oral health experts who study mouth sores and canker sores, as well as cold sores, have concluded that mouth sores and canker sores are terms that can be used interchangeably. They are different terms for the same problem, describing painful spots inside a person’s mouth. Canker sores and cold sores, however, are not the same thing, even though many people confuse canker sores with cold sores. A dentist or doctor can help you determine which condition you’re dealing with, which is important, because treating the wrong condition may alter the effectiveness of the treatment fore each type of sore.

Mouth sores and canker sores are shallow ulcers inside the mouth, whereas cold sores are blisters on the exterior of the mouth. Canker sores can be caused by stress or the consumption of highly acidic foods, such as lemons and pineapple — fresh pineapple, in particular. Certain medications, including chemotherapy, certain arthritis medication and some sleep aids.

Canker sores can also be indicators of more serious health conditions, including cancer and non-herpes infections. Recurrent mouth sores and canker sores can be caused by a deficiency of various vitamins, such as iron and zinc. They may also suggest Crohn’s disease or a gastrointestinal tract disease.

Symptoms of mouth sores and canker sores include painful gums and sores on the tongue, soft palate, or inside the cheeks. If the mouth sores are indicators of a more serious health condition, one may suffer from a fever, swollen lymph nodes, or fatigue. These symptoms may be relieved with an antimicrobial mouth rinse, ointment, or a prescription. To avoid suffering from canker sores, even if you’ve had them in the past, avoid eating highly acidic foods and maintain good, regular dental hygiene.

Cold sores, or fever blisters, are caused by the herpes simplex virus (HSV). If there is an open wound, HSV can enter through the break in the skin. There also may be tingling or burning in the mouth as a warning of sorts when an outbreak is just starting.

The virus that causes cold sores, herpes simplex, is contagious. It is spread when people who are infected share drinking glasses or eating utensils with someone who is not infected. Unlike mouth sores and canker sores, which are generally painful but discreetly tucked away inside the mouth, rarely to be seen, cold sores are painful and rather noticeably perched outside the mouth.