These very common sores are often confused because they both usually occur in or around the mouth. But there are crucial differences—in appearance, causes, and specific locations.

Canker sores have bothered humanity since ancient times. Hippocrates coined the medical term for them—aphthous stomatitis—in the fourth century B.C. These crater-like lesions can occur on or under the tongue or inside the cheek. They have not been proved to have a viral origin, nor are they known to be contagious or a sign of an underlying disease.

Cold sores are tiny, unsightly, and often painful blisters that occur most frequently on the lips and adjacent skin, though occasionally on gums or the nose. Any reactivation of cold sores is usually, but not always, signaled 24 to 48 hours prior to an outbreak by an itching or tingling sensation in the lips. A small red area develops, followed by a blister or group of tiny blisters that fill with liquid.

Symptoms of Canker Sores and Cold Sores

Canker sores

  • Small white or yellow sores ringed by a red area on the tongue or inside the lips or cheek
  • Pain or tingling preceding the appearance of the sore
  • Local pain when eating and talking, especially during the first two or three days

Cold sores (also called fever blisters)

  • Painful, itchy, fluid-filled blisters that commonly occur on the lips
  • Burning, itching, and/or tingling sensation often preceding the blister by a few days
  • Rupture of the blisters within hours, followed by crusting

What Causes Canker Sores and Cold Sores?

No one is sure what causes canker sores, and there are no known remedies. Canker sores seem to be brought on by stress in some people; stress can also be a side effect. Heredity may play a role, and some women find that the sores recur with menstrual periods. Some people believe that irritation from such foods as chocolate, salted nuts, or potato chips can cause an outbreak or that food allergies can cause the problem. There’s no proof, but it certainly won’t hurt to follow your hunches.

Another suspect is trauma—the kind that comes from biting your tongue or the inside of your cheek, or from using a hard-bristled toothbrush, having a jagged tooth, rough dentures, or being burned from hot food or liquids.

Cold sores, on the other hand, are caused by the herpes simplex virus (HSV)—usually by HSV Type 1, which is different from the Type 2 virus more commonly associated with genital herpes. The infection is contagious, but most people have already contracted the virus by early adulthood (though often with no symptoms). The virus lies dormant in the body until it is triggered by factors such as a cold, fever, fatigue, sunlight, or emotional stress—though in many cases the cause of the virus being activated isn't known.

What If You Do Nothing?

Painful and irritating as they are, canker sores usually go away in 5 to 15 days, with or without treatment.

Similarly, cold sores, although unsightly, pose no health threat and will clear up on their own within 7 to 10 days.

Home Remedies for Canker Sores and Cold Sores

Canker sores

The Food and Drug Administration (FDA) has approved the first drug for canker sores, called amlexanox (Aphthasol). This prescription oral paste, intended only for canker sores, has been shown to ease pain and accelerate healing by a day or two. The following remedies may also help ease discomfort.

  • Ice it. Apply crushed ice to the sore. This will numb the pain and provide some relief.
  • Avoid spicy foods. Abrasive, acidic, and spicy food can irritate the sores.
  • Brush carefully. Using a soft brush will minimize irritation.
  • Try over-the-counter pain relief. If canker sores become very painful, ask your pharmacist to recommend an anesthetic drug or protective gel to reduce pain and inflammation.
  • Apply a wet black tea bag to the sores. This will help canker sores to heal faster.

Cold sores

The first over-the-counter medication for healing cold sores, called Abreva, was approved by the FDA. By applying this topical cream as soon as the tell-tale tingling of a cold sore occurs, you may be able to prevent the blister from developing or, if it does appear, speed up the time it takes to heal (though the drug won’t help everyone). For severe outbreaks, prescription medications are likely to offer the most benefit.

Other products (such as the amino acid lysine) have been suggested for treating cold sores, but there is no evidence that they work.

The following remedies may help relieve the discomfort of a cold sore.

  • Rinse with salt water. Rinse your mouth several times a day with a cup of warm water to which you’ve added a half teaspoon of salt.
  • Try ice. Applying an ice cube to the infected area may help relieve pain. Wrap an ice cube in a damp washcloth and keep it on the area for five minutes. Reapply it every hour.
  • Apply an ointment. An over-the-counter anesthetic ointment can help relieve pain.
  • Don’t pick. Do not squeeze, pick, or pinch a blister or scab. A light coating of petroleum jelly on the scab will prevent cracking and bleeding.
  • Wash carefully. This will help prevent infection. Avoid touching your eyes, genital area, or another person.


Canker sores

It’s not clear how to prevent canker sores, but the following steps can help.

  • Keep the mouth clean and healthy. Brush at least twice daily and floss regularly. And consider switching tooth cleansers: a study conducted in Norway suggested that a detergent found in most toothpastes, sodium laurel sulfate, can aggravate canker sores. If you have recurrent sores, try switching to a tooth powder, baking soda, or other dentrifice without this ingredient.
  • Stop biting. Any mouth injury can get infected, so if you unconsciously bite the inside of your cheek, try to break the habit.
  • Stay away from anything that can hurt the lining of the mouth. This includes hard-bristled toothbrushes, toothpicks and bones in meats.
  • Determine if specific foods trigger attacks. Avoid those foods that seem to cause problems.

Cold sores

  • Use sunblock. Outbreaks due to sun exposure can be prevented by applying sunscreen with a sun protection factor (SPF) of 15 on the lips before going outside and reapplying it frequently during the day.
  • Avoid touching the blisters. Touching the blisters and then other people is a possible way of spreading the virus. Kissing is one of the most common ways this transmission occurs.
  • Don’t share. During an outbreak, don’t lend personal items such as towels, razors, cups, or toothbrushes.
  • Avoid hard, crunchy or spicy foods.
  • Consider medication. If you get frequent outbreaks, speak with your physician about taking an antiviral drug for prevention.
  • Avoid toothpaste that contains sodium lauryl sulfate and other irritating ingredients.
  • Quit smoking and avoid drinking alcohols.

Beyond Home Remedies: When To Call Your Doctor

Canker sores

Contact your physician if the pain becomes severe, you’re unable to drink adequate fluids, the mouth ulcers increase to four or more in number or last longer than two weeks, or if a fever develops. If a canker sore is caused by your dentures or braces, consult your dentist to eliminate the problem. Also contact your physician if you develop canker sores more than two or three times a year.

Cold sores

Contact your physician if you develop a fever, if your cold sores last longer than two weeks despite treatment, or if cold sores recur frequently during the course of a year.

What Your Doctor Will Do

Canker sores

After a careful examination, your physician may apply a topical anesthetic to relieve pain or may prescribe medications to reduce inflammation and prevent pain. A prescription for amlexanox (Aphthasol), a canker sore medication, can be worthwhile if your lesions are very painful and if they tend to recur.

Cold sores

After a careful examination, your physician may prescribe penciclovir (Denavir), an antiviral cream, to help speed the healing of existing sores. If you get frequent cold sores, ask your doctor about oral acyclovir (Zovirax), a prescription antiviral medication that can help reduce the severity and duration of cold sores if taken as soon as you notice the early warning signs of itching and tingling. Two related drugs, famciclovir (Famvir) and valacyclovir (Valtrex), are also used as preventive agents.


The Complete Home Wellness Handbook

John Edward Swartzberg, M.D., F.A.C.P., Sheldon Margen, M.D., and the editors of the UC Berkeley Wellness Letter

Updated by Remedy Health Media

Publication Review By: the Editorial Staff at

Published: 27 Oct 2011

Last Modified: 04 Nov 2014