Cold Sores Vs Canker Sores: How To Tell Them Apart

Cold sores and canker sores are two conditions that are often confused because they sound alike and both affect the mouth area. However, despite their similarities in name and location, they are entirely different in terms of cause, appearance, symptoms, and treatment. People who experience recurring sores near or inside the mouth might be unsure whether they’re dealing with a cold sore or a canker sore, and knowing the difference is essential for proper care.

One of the key distinctions lies in where they appear. Cold sores generally show up on or around the lips, while canker sores occur inside the mouth, such as on the tongue, gums, inner cheeks, or roof of the mouth. Misidentifying these two can lead to ineffective treatment and unnecessary discomfort, so let’s break down the major differences, causes, and how to manage each one safely and effectively at home.

What are cold sores?

Cold sores, otherwise known as fever blisters, are caused by the herpes simplex virus (usually HSV-1). Once you’ve been infected, the virus remains in your body for life and may reactivate during times of stress, illness, hormonal changes, or sun exposure¹. These sores typically start with a burning or tingling sensation before a blister forms. Eventually, the blister bursts and forms a crust before healing.

They are highly contagious and can spread through direct contact, such as kissing or sharing utensils. This makes it important to avoid skin-to-skin contact when a sore is active, even if it’s in the early tingling stage.

What do cold sores look like?

Cold sores usually begin as small blisters grouped together on or around the lips. These blisters may burst, ooze, and crust over within a few days. The entire episode generally lasts between 7 to 10 days. Some people may also experience swollen lymph nodes, fever, or sore throat² during their first outbreak.

They often return to the same location during recurrences and can become painful, especially if cracked or irritated. Triggers such as UV exposure or fatigue can increase the likelihood of a recurrence.

What are canker sores?

Canker sores, on the other hand, are not caused by a virus and are not contagious. These small ulcers form inside the mouth, often on the soft tissues, and can be triggered by a variety of factors³, such as minor injuries from dental work, harsh toothbrushing, trauma, and certain acidic foods, or stress. Vitamin deficiencies, especially B12, iron, and folic acid, may also increase the risk.

Canker sores tend to heal on their own within one to two weeks and do not leave scars. They are more common among adolescents and young adults and may occur sporadically or in clusters.

What do canker sores look like?

Canker sores appear as round or oval ulcers with a yellow or white centre and a red border. Unlike cold sores, they do not involve blisters and are limited to the inside of the mouth. They can make eating, drinking, or speaking uncomfortable, especially if located in high-friction areas like the tongue or inner lip.

In some cases, people with frequent or unusually painful canker sores may benefit from seeing a skin dermatologist in Singapore, particularly if the sores interfere with daily life or don’t heal as expected.

Key differences at a glance

Feature	Cold Sores	Canker Sores
Cause	Herpes Simplex Virus (HSV-1)	Non-viral (trauma, stress, deficiencies)
Location	Outside the mouth (usually lips)	Inside the mouth (cheeks, tongue, gums)
Contagious	Yes	No
Appearance	Fluid-filled blisters	Small yellow or white ulcers
Pain	Often painful, especially when burst	Painful, especially when eating/speaking
Healing Time	7–10 days	1–2 weeks

Managing cold sores

Treating cold sores early is crucial for shortening the duration and easing symptoms. Over-the-counter creams with antiviral ingredients like acyclovir can be effective if applied at the tingling stage. In more severe or frequent cases, a doctor might prescribe oral antiviral medication² to reduce outbreaks and speed up healing.

It’s also important to avoid touching the sore, wash your hands regularly, and avoid sharing personal items such as lip balm, razors, or utensils. Using a lip balm with sunblock can help prevent future outbreaks, especially for those triggered by sun exposure.

Managing canker sores

Canker sores often don’t require medical treatment, but there are remedies that can help with pain and healing. Saltwater rinses, mouthwashes, or over-the-counter topical gels containing benzocaine³ can offer relief. Avoiding spicy or acidic foods may also reduce irritation.

Some people may notice a pattern with their canker sores, such as outbreaks following stress or poor nutrition. In these cases, managing stress and adopting a balanced diet might reduce frequency. For persistent or recurrent ulcers, especially large ones that don’t heal within three weeks, seeking advice from a dermatologist is recommended for further evaluation.

When to see a dermatologist

While both cold sores and canker sores are usually mild and self-limiting, recurring episodes or unusually severe symptoms might signal an underlying issue. This includes:

Sores that last longer than three weeks
Frequent outbreaks (more than three times a year)
Difficulty eating or drinking
High fever or fatigue with oral sores
Unusual sores spreading beyond the lips or mouth

A qualified dermatologist can offer a proper diagnosis, rule out other conditions like autoimmune disorders or nutritional deficiencies, and prescribe more effective medications if needed. For those already following a morning and night skincare routine, adding oral health awareness can round out a comprehensive care approach.

Conclusion

Cold sores and canker sores might seem similar, but they’re very different in cause, appearance, and treatment. Cold sores are contagious and linked to the herpes virus, while canker sores are non-contagious ulcers triggered by factors like stress or injury. Knowing which one you’re dealing with can make treatment easier and more effective.

If you’re experiencing frequent or severe mouth sores and want expert help, consider reaching out to Angeline Yong Dermatology. Offering cosmetic, surgical, and medical treatments in Singapore, we’re well-equipped to provide personalised care to help you look and feel your best.

References

Cold sores. HealthHub. (n.d.). https://www.healthhub.sg/a-z/diseases-and-conditions/cold-sores

Cold sore. Mayo Clinic. (2024, January 5). https://www.mayoclinic.org/diseases-conditions/cold-sore/symptoms-causes/syc-20371017

Canker sore (Aphthous ulcer): What it is, causes & treatment. Cleveland Clinic. (2025, June 25). https://my.clevelandclinic.org/health/diseases/10945-canker-sores

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Cold Sores Vs Canker Sores: How To Tell Them Apart