Cold sore vs canker sore on lip

These two mouth irritants aren’t the same thing. Find out how to tell which one you might have and, better yet, what to do about them.

Although sores in and around the mouth may be embarrassing, they shouldn’t be, because they’re very common. At least half the population gets canker sores, and about the same amount gets the virus that can cause cold sores. But the two types of sores are completely different, so here’s what you need to know to tell them apart.

1. Known versus unknown causes

Cold sores, also called fever blisters or oral herpes, are most often caused by the herpes simplex virus type 1, which people usually pick up in childhood. Although the virus then settles into bundles of nerve cells in the body and may never bother you again, it stays with you for the rest of your life and can pop up from time to time.

The causes of canker sores, or aphthous ulcers, are less known. It may be that the immune system mistakenly attacks the mucous cells of the mouth. Canker sores are also linked to Crohn’s disease and other systemic conditions, including nutritional deficiencies; they may also be caused by stress, hormonal shifts or allergic reactions to certain ingredients in food or toothpaste.

2. Oozing blister outside the mouth versus painful ulcer inside

The way cold sores and canker sores appear is very different, too. Cold sores occur most often outside your mouth, in the corners or on your lip. If you find one inside, it’s usually on harder tissue, such as your gums or the roof of your mouth. Cold sores form blisters that then break open, ooze and crust over. You may feel a tingling or burning sensation before a blister appears.

Canker sores are small and round or oval and develop in the soft tissue inside your mouth. You might get one behind your lip, on the inside of your cheek or under your tongue. They’re red, flat and often have a whitish top. If they become large or painful, they may prevent you from comfortably eating and drinking.

3. Contagious versus not contagious

Perhaps the most important thing to know is whether these conditions can be passed to others. Cold sores are highly contagious, especially when you have an active one — but you can transmit the virus even when you don’t. It’s spread by saliva or skin contact. If you touch your cold sore, wash your hands right away to avoid spreading the virus to other parts of your skin.

Canker sores, on the other hand, aren’t contagious, so you don’t have to worry about giving them to anyone else.

If they do show up, what’s the best treatment?

Most of the time, both types of sores will heal by themselves within a week or two, but medications are available to ease their effects.

For cold sores, taking an antiviral medication at the earliest sign may reduce pain and shorten the outbreak, according to Sharon Orrange, MD, an internal medicine physician at Keck Medicine of USC and clinical associate professor of medicine at the Keck School of Medicine of USC. The type of medication you choose, however, can have an impact.

“Topical medications for cold sores don’t work that well, are expensive and usually require frequent daily applications,” Dr. Orrange says. “But evidence shows that drugs such as valacyclovir effectively reduce both healing time and the duration of pain.”

For small, painful canker sores, she suggests using an over-the-counter numbing medication. But if you have large painful canker sores that are making it difficult to eat, you should ask your physician for help.

“Prescription pastes and gels are available that can help speed your healing,” Orrange says. “Also, see your doctor if your canker sores recur, because the recurrence could indicate celiac disease, inflammatory bowel disease or HIV.”

Although they’re annoying, sometimes painful and can’t be cured, there’s good news about canker and cold sores: In the majority of cases, both are relatively harmless and don’t have lasting consequences.

Topics

canker sores

celiac disease

cold sores

Crohn’s disease

Dr. Sharon Orrange

Tina Donvito is a freelance writer covering health, culture, travel and parenting.

If you've ever had a sore on or near your mouth, you've likely thought to yourself: Is this a canker sore or a cold sore, and what's the difference? Here are three significant differences of a canker sore vs. cold sore to help you determine your next steps for treatment.

1. Appearance

The first way to differentiate a canker sore vs. cold sore is by appearance. As the Mayo Clinic explains, canker sores — also called aphthous ulcers — appear inside the mouth. They develop in soft tissues, such as in the cheeks, gums, under the tongue or on the tongue. Canker sores look like small white or yellow circles surrounded by a red border and may cause discomfort when you eat or drink.

Cold sores, on the other hand, usually appear on or around the lip, as the Mayo Clinic explains. A cold sore often looks like a cluster of blisters, and they can eventually burst, causing oozing and crusting.

2. Causes

Canker sores and cold sores have different underlying causes. According to the American Dental Association, the exact cause of canker sores is unknown. Experts speculate that they may happen as a result of immune issues, mouth trauma, bacteria or viruses.

Cold sores result directly from the herpes simplex virus (HSV-1), according to the Mayo Clinic. This virus is dormant until triggered, which is when you might experience a tingling or burning sensation in your mouth and the development of a sore. Several factors can trigger the recurrence of a cold sore:

• Stress
• Other viral infections
• Fatigue
• Exposure to sun or wind
• Hormonal changes
• Fever

3. Treatments

Both canker sores and cold sores usually heal on their own. Minor canker sores typically take a week or two to heal, according to the Mayo Clinic, while cold sores may take two to four weeks. Cold sores usually do not leave scars; however, major canker sores have the potential to cause scarring.

If your symptoms last longer than you'd like, you can also discuss treatment options with a medical or dental professional. For canker sores, if they are unusually large, clustered or painful, your doctor or dentist may suggest mouthrinses, topical ointments or oral medication.

Because cold sores are caused by HSV-1, the American Academy of Dermatology (AAD) suggests treating them with antiviral topical or oral medications. If you are experiencing discomfort, your doctor or dentist may also prescribe a pain-relief medication. In addition, the AAD strongly encourages the use of sunscreen during an outbreak, as sun exposure can affect the healing of the sore.

Another important note: Unlike canker sores, cold sores are contagious, according to the Mayo Clinic. Therefore, to prevent spreading the virus, you should not share utensils or any other items that touch the mouth.

The easiest way to tell the difference between a canker sore and a cold sore is by its location. If the sore is in your mouth, it's likely a canker sore. If it's outside the mouth, it's probably a cold sore. If you aren't sure — don't worry. See your doctor or dentist so that they can determine what it is and recommend the proper treatment.

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