Cold Sore or Canker Sore? How to Tell the Difference and Treat Each One

The quickest way to tell a cold sore from a canker sore is where it is. A cold sore sits on the outside of the lip, starts with a tingle and turns into a cluster of small fluid filled blisters that crust over. It’s caused by the herpes virus and is contagious. A canker sore sits inside the mouth, on the soft skin of the cheek, inner lip, gums or tongue, and is a single round ulcer with a white or yellow centre and a red border. The American Dental Association confirms that canker sores are not contagious, while cold sores are. Because the causes are different, so is the care: a cold sore needs care aimed at the virus and your immunity, like a beeswax or propolis ointment at the first tingle, while a canker sore needs a calm mouth and a look at your diet and gut balance, like raw honey, salt water and cutting back on sugar. Fever blisters are simply another name for cold sores. For the full care of each, see our guides to cold sores, herpes on lips and canker sore treatment.

The short version

Outside the lip, blisters, tingling first: most likely a cold sore (herpes). Contagious.
Inside the mouth, one round white ulcer with a red rim: most likely a canker sore. Not contagious.
Cold sore care: beeswax or propolis ointment at the first tingle, SPF lip balm, a strong immune system.
Canker sore care: raw honey, salt water rinses, SLS free toothpaste, less sugar, alcohol and bread.
Any sore that hasn’t healed in two to three weeks needs a dentist or doctor to look at it.

Cold Sore vs Canker Sore at a Glance

	Cold sore (fever blister)	Canker sore
Where	Outside the mouth: lip border, corner of the mouth, under the nose, chin	Inside the mouth: inner lip, inner cheek, gums, tongue, floor of the mouth
Looks like	A cluster of small blisters that burst, weep and crust	A round, shallow ulcer with a white or yellow centre and a red border, no blister
First sign	Tingling, itching or burning on the lip	A sore or burning spot inside the mouth
Cause	Herpes simplex virus, usually type 1	Not fully known: immune reaction, bacterial imbalance, stress, small injuries, low B12, certain foods
Contagious?	Yes, from the first tingle until fully healed	No
How long	About 7 to 10 days	About 1 to 2 weeks
Comes back?	Yes, in the same area, as the virus stays in the nerve	Often, but in different spots

How to Tell If It’s a Cold Sore

A cold sore is herpes on the lips. After a first infection, the herpes simplex virus sleeps in a nerve and wakes up from time to time, often after stress, illness, sunlight or a bad night’s sleep. These are the signs:

It starts with a tingle. A day or so before anything shows, the lip tingles, itches or burns.
It’s on the outside. Usually on the border of the lip, but it can also appear under the nose, on the chin or at the corner of the mouth.
It’s a cluster of blisters. Small, clear, fluid filled blisters appear close together, then burst and form a yellow or brown crust.
It comes back in the same place. Many people get their cold sore in exactly the same spot each time.

Fever blisters are the same thing as cold sores, just a different name. You can read more in our article on fever blisters, and learn to spot the early warning signs in herpes outbreak symptoms.

How to Tell If It’s a Canker Sore

Canker sores, also called aphthous ulcers, are described by the American Dental Association as small, creamy white ulcers with a red border that are quite painful. These are the signs:

It’s inside the mouth, on the soft, moving skin: the inside of the lip or cheek, under or on the tongue, the gums or the floor of the mouth.
It’s an ulcer, not a blister. Researchers describe a yellowish white base framed by a red halo. It’s flat or slightly sunken.
It’s usually one or a few, each round or oval.
It stings when you eat, especially acidic, salty or spicy food.
It’s not contagious, so you can’t pass it on by kissing or sharing a cup.

For a sore on the tongue in particular, see canker sore on tongue, and for sores in several places in the mouth, read our guide to mouth ulcers.

Can a Cold Sore Be Inside the Mouth?

Yes, occasionally, and this is where it gets confusing. Herpes can appear inside the mouth, but usually on the firm skin that sits tight over bone: the gums and the roof of the mouth. It then looks like a small group of tiny blisters or pinpoint sores, rather than one round ulcer. A first herpes infection, often in young children, can cause painful sores all over the gums and inside the mouth, with fever. Canker sores, on the other hand, almost always form on the soft, loose skin of the cheeks, inner lips and tongue.

A canker sore never appears on the outside of the lip. So if the sore is on the skin of your lip, it’s almost certainly a cold sore.

Are Canker Sores Herpes?

No. This is one of the most common questions, and the answer is clear. Canker sores are not caused by the herpes virus and are not a sexually transmitted infection. The American Dental Association explains that the cause of canker sores is uncertain, with an immune reaction, stress, fatigue and allergies all playing a part. In my view, most canker sores come from an imbalance of bacteria or fungus in the body that your system can’t fully fight off. Research supports part of this: people with canker sores have a different mix of mouth bacteria than people without them.

How to Treat a Cold Sore

A cold sore is a virus coming to the surface, so the care is about stopping it early and keeping your immunity strong.

Act at the first tingle. The amount of virus is highest in the first 24 hours, so this is when care makes the biggest difference.
Use a beeswax or propolis ointment. A propolis lip cream healed cold sores in a median of 3 days in a large trial. I use a beeswax ointment at the first tingle, and in my experience the cold sore is usually gone in about two days.
Try honey. Honey made lip outbreaks 35% shorter in a trial.
Cover it with a cold sore patch once a blister forms, so you don’t touch it or spread it.
Protect your lips from the sun with an SPF lip balm. Sunscreen prevented every sunlight triggered cold sore in a trial.
Don’t kiss or share cups, towels or lip balm until it has fully healed.
Support your immunity with protein, fruit, vegetables, sleep and less stress.

For cold sores: the ointment I use at the first tingle

The Aromafisis beeswax ointment with oregano is handmade from olive oil, beeswax, oregano oil, clary sage and mastic oil, with no preservatives. It’s usually gone within about two days.

See the beeswax ointment

Not an affiliate link. For cold sores on the outside of the lip only, not for canker sores inside the mouth. Comfort care, not a cure.

For pharmacy options, see cold sore remedies over the counter, and to keep them from coming back, read how to avoid a herpes outbreak.

How to Treat a Canker Sore

A canker sore isn’t a virus, so antiviral care won’t help. The care is about calming the mouth, letting the ulcer heal and rebalancing what’s going on inside.

Dab raw honey on it. In a trial, honey healed canker sores faster and eased pain and redness better than a steroid cream and a protective paste.
Rinse with salt water or baking soda three or four times a day.
Oil pull with coconut oil in the morning to rebalance the bacteria in your mouth. Coconut oil pulling reduced harmful mouth bacteria about as well as a chlorhexidine mouthwash.
Switch to an SLS free toothpaste. There’s limited evidence it helps people who get canker sores often.
Avoid acidic, spicy, salty and crunchy food until it heals.
Look at your diet if they keep coming back. Too much sugar, alcohol or bread can push your system into an unregulated state. Cutting back is often the first step to fewer canker sores.
Consider vitamin B12. In a trial, 74% of people taking B12 every night became free of canker sores, compared with 32% on a placebo.

For canker sores: finding it hard to stay away from sugar?

Gluco-Control is a plant based supplement with enzymes, mushroom extracts and probiotics, taken before meals. It’s designed to support healthy blood sugar and curb sweet cravings, which can make cutting back on sugar a lot easier while you rebalance.

See Gluco-Control

This is an affiliate link. If you buy through it, Home Remedy Shop may earn a small commission at no extra cost to you. A supplement works alongside dietary changes, not instead of them.

For the full plan, including my morning apple cider vinegar shot and a gentle detox option, see our guide to canker sore treatment.

What Not to Mix Up

Don’t put a cold sore ointment inside your mouth. Lip products aren’t made for the inside of the mouth.
Don’t use harsh, drying products on either. Alcohol, toothpaste or undiluted essential oils sting and slow healing.
Don’t worry about spreading a canker sore. You can’t. But do be careful with a cold sore, especially around babies, pregnant women and people with a weak immune system.

Other Sores That Look Similar

A pimple on the lip: a single raised bump with a white head, often with a hair follicle, no tingling beforehand.
Angular cheilitis: painful cracks in the corners of the mouth, not blisters.
Oral thrush: creamy white patches that wipe off to leave a red area.
Hand, foot and mouth disease: sores in the mouth together with spots on the hands and feet, mostly in children.

When to See a Dentist or Doctor

Any sore that hasn’t healed after two to three weeks. See a dentist for sores inside the mouth, or your GP or a dermatologist for sores on the lip.
A cold sore near the eye, or a painful red eye. See an eye doctor the same day.
Canker sores that keep coming back. Ask your GP for a blood test for vitamin B12, iron and folate.
Mouth sores with stomach pain, diarrhoea or weight loss. A gastroenterologist can check for coeliac disease or Crohn’s disease.
A first cold sore with fever, sores all over the mouth, or a child who won’t drink. See your GP.
A baby with a blister or sore and a fever. Go to the emergency room straight away.

Knowing exactly what you’re dealing with is what lets you treat it the right way naturally. For an overview of natural care for all types of herpes, see our guide to natural herpes remedies, and for sores in the genital area, genital herpes outbreak treatment at home.

Frequently Asked Questions

How can I tell if it’s a cold sore or a canker sore?

Look at where it is. A cold sore is on the outside of the lip and starts as a cluster of small blisters after a tingle. A canker sore is inside the mouth and is a single round ulcer with a white or yellow centre and a red border.

Are canker sores herpes?

No. Canker sores aren’t caused by the herpes virus, aren’t contagious and aren’t a sexually transmitted infection. Cold sores are caused by herpes.

What’s the difference between a canker sore and a fever blister?

A fever blister is another name for a cold sore. It’s caused by the herpes virus, appears on the outside of the lip and is contagious. A canker sore is an ulcer inside the mouth and isn’t contagious.

Can you get a cold sore inside your mouth?

Occasionally. Herpes inside the mouth usually shows up as tiny blisters or pinpoint sores on the gums or the roof of the mouth. A single round ulcer on the inner cheek, inner lip or tongue is much more likely to be a canker sore.

Do you treat a cold sore and a canker sore the same way?

No. A cold sore needs early care for the virus, like a beeswax or propolis ointment at the first tingle. A canker sore needs a calm mouth, like raw honey, salt water rinses and an SLS free toothpaste, and a look at your diet if it keeps coming back.

This article is for general information and does not replace a diagnosis. If you’re not sure what a sore is, or it doesn’t heal, see a dentist or doctor.

Veronique Cleas D'erckenteel

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