A little irritation develops near or inside your mouth, and you start to wonder what\u2019s wrong. It hurts a lot more than it should, considering the small size. It seems to last awhile, and you can\u2019t figure out whether it\u2019s a cold sore or canker sore.\nSo, what exactly is the difference between a cold sore and a canker sore? Let\u2019s dive in. Fortunately, it\u2019s not too complicated.\nUPMC AnywhereCare gives you easy online access to health care providers. Learn more today.\u00a0\nCold Sore vs. Canker Sore\nWhat is a cold sore?\nOutside of the mouth is where you\u2019ll find a cold sore, sometimes called a fever blister. It usually appears as one or several red, blistered areas on your lips. The blisters often will break open causing an open sore, or ulcer.\nWithin a few days, a scab will form. Some areas of the mouth take longer to heal because they frequently stretch when you talk, eat, or yawn.\nWhat causes cold sores?\nWhat causes cold sores is the herpes simplex virus and, unfortunately, the sores are contagious when they\u2019re open. That means the virus can be spread when sharing utensils, drinks, or towels, and by kissing.\nThe herpes virus stays in your body and can cause cold sore outbreaks at any time. Often, they\u2019re triggered by things such as extreme temperatures, exhaustion, stress, or a weakened immune system.\nWhen you feel a cold sore coming on, usually indicated by a tingling or itching on the affected area, consider anything out of the ordinary that you\u2019ve been experiencing, as this could be your trigger. Once you figure out what your triggers are, you can try to avoid them. Use sunblock if a cold sore is caused by sun exposure or take a few minutes to relax if stress is a trigger for you.\nHow to treat a cold sore\nWhile there\u2019s no cure for cold sores, treatment can help to shorten the lifespan or weaken the severity. Some people start treatment when they first notice symptoms. A cold sore treatment is for symptom relief, and can include an antiviral topical ointment, oral antiviral medication, or over-the-counter topical anesthetic or anti-inflammation agent.\nYour first cold sore can take up to three weeks to heal, but later ones may disappear in a week or two. While there\u2019s not usually a reason to go to the doctor for a cold sore, your doctor can test for the virus with a swab and culture and prescribe antiviral medication.\nWhat are canker sores?\nCanker sores are found on the inside of the mouth, including the lips, cheeks, and tongue. They\u2019re small ulcers that could be caused by a thing such as:\n\nFood allergies\nA weakened immune system\nStress\nMouth injury (like biting your tongue or cheek)\nSome medicines\nViruses\/bacteria\nIrritation caused by orthodontic braces\n\nThe sores usually have a red base and may be covered by a white or yellow layer.\nHow to treat canker sores\nCanker sores aren\u2019t contagious, and they are not easily visible to others. They can be painful, though.\nYou might try an oral \u00a0pain reliever since ointments are difficult to keep in place when the sore is inside your mouth. Keeping your mouth clean by brushing regularly can help, and anesthetic mouth rinse can help ease the pain too. Some people find it helpful to avoid spicy, acidic, or salty foods while it\u2019s healing, which can take up to two weeks.\nThere\u2019s no reason to go to the doctor unless the sores return frequently or are large.\nSo, what is the difference between canker sore versus cold sore? Location, location, location! Cold sores are usually on the edge of the lips, while canker sores are inside the mouth. Cold sores are contagious and can be treated with antiviral ointments and pain relievers, while canker sores require only pain relief. And both can last a few weeks.\nFor more information on treating oral sores or to find a doctor, contact UPMC.