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Identifying Cold Sores vs. Fever Blisters vs. Canker Sores

Cold sores, also known as fever blisters, and canker sores, are both blisters that develop in the mouth. Although cold sores are more commonly found on the lips and surrounding the mouth. Cold sores are contagious and caused by the herpes virus. Canker sores are not contagious and have many potential causes.

The treatment for cold sores and canker sores is also different. This is why telehealth services are especially handy. An online doctor can look at your blisters and discuss your symptoms. They can give you a proper diagnosis and recommend treatment.

What Are Cold Sores?

Cold sores are blisters that form in the mouth, or more commonly on the lips or around the mouth. They are often grouped in patches and go through stages. Initially, you may feel a tingling sensation, followed by a blister that pops and then crusts. The blisters heal without leaving scars.

Causes of Cold Sores

Cold sores are caused by an infection with the herpes virus. More commonly, it is herpes simplex virus type 1 (HSV-1), but herpes simplex virus type 2 (HSV-2) can also cause cold sores.

Herpes virus is very contagious. More than half the population worldwide has been exposed to HSV-1, but that does not mean everyone develops symptoms.1,2 If exposed, you may experience an outbreak and flu-like symptoms.

After this initial outbreak resolves, the herpes virus remains dormant in your nervous system. Stress, other infections, or a weaker immune system can allow the herpes virus to cause another outbreak. The symptoms from repeated outbreaks are typically not as severe as the initial outbreak. Getting an online diagnosis is a simple way to determine whether you have cold sores caused by the herpes virus and how to minimize future outbreaks.

A close up of a cold sore.

What Are Fever Blisters?

Fever blister is another name for cold sores. They are the same thing. With an initial outbreak of fever blisters, many people have a fever and other flu-like symptoms, hence the name fever blister.

A fever blister is a small, inflamed area of blisters, typically found on the lips or around the mouth. You may notice a tingling or itching sensation in the area before the blister develops. Then the blister forms and seeps clear liquid. Eventually, it crusts.

Fever blisters (cold sores) can cause recurrent outbreaks in susceptible people. Talk to an online doctor about your fever blisters to learn whether getting a prescription online for an antiviral medication would help prevent future outbreaks. Applying antiviral creams or taking medications at the first sign of a fever blister (tingling sensation) can slow the virus replicating and potentially prevent a cold sore from developing.3

Causes of Fever Blisters 

Fever blisters, since they are the same as cold sores, are caused by the herpes simplex type 1 (HSV-1) and type 2 (HSV-2) viruses. Herpes viruses are contagious and spread via direct contact with a person who is infected. This person may not have any symptoms and therefore not know they are infected. This is why over half the population is infected with herpes.

What Are Canker Sores?

Canker sores, also known as aphthous ulcers, are small blisters or sores that develop inside your mouth. They can be found on the gums, the roof of the mouth, on or below the tongue, or inside the cheeks.

Like with cold sores, you may notice a tingling sensation before a canker sore develops. Because the two conditions have overlapping symptoms, a proper diagnosis is essential. An online doctor can look inside your mouth using your camera and make a diagnosis. They can write an online prescription if it is needed to speed up your recovery and prevent future outbreaks.

Causes of Canker Sores

Canker sores are not contagious, though their cause is unknown. There are many potential causes, but they are not related to the herpes simplex virus.

Canker sores can be classified as:4,5

  • Minor: These canker sores are smaller, oval in shape, and typically resolve on their own within two weeks.
  • Major: These canker sores are larger, deeper, irregular, and last longer than two weeks. They are more likely in people whose immune system is suppressed due to illness or medication and may cause scarring.
  • Herpetiform: These are more common in older adults. Multiple tiny blisters converge to form a larger sore. Herpetiform canker sores can last for a week to a month.  

Potential triggers for canker sores include:6

  • Ill-fitting dentures
  • Biting your cheek or hitting your gums with your toothbrush
  • Vitamin deficiencies such as vitamin B-12, zinc, folic acid, or iron
  • Sensitivity to sodium lauryl sulfate in toothpastes and mouthwashes
  • Hormonal fluctuations
  • Immunodeficiency or suppression
  • Stress
  • Food sensitivities
  • Helicobacter pylori infection
A close up of a canker sore

Key Differences Between Cold Sores, Fever Blisters, and Canker Sores

Cold sores (fever blisters) more commonly occur on the lips and face, though they can be in the mouth. Aphthous ulcers are found inside the mouth.

Cold sores are blisters that form in groups and crust after they break. Canker sores are ulcers inside the mouth that heal from the outside as long as they don’t get infected.

Cold sores are caused by the herpes virus, a contagious virus that readily spreads from person to person. Canker sores are not contagious and have several potential causes.

How To Treat Cold Sores, Fever Blisters, and Canker Sores

Potential treatment options for cold sores (fever blisters):

  • Antivirals: Antiviral medications block the virus from replicating.
  • Cold: Try a cold compress or ice pack to reduce pain.
  • Pain and symptom-relieving creams: Docosanol, benzocaine, prilocaine, lidocaine, glycine, zinc oxide, and zinc sulfate creams may reduce symptoms and speed healing.
  • Sunscreen: Sunscreen can help if ultraviolet light exposure triggers your outbreaks.

Maintaining good oral hygiene is the most important factor in healing canker sores. To prevent future outbreaks, try to avoid mouth trauma. Potential treatment options for canker sores:7

  • Avoid foods, toothpastes, and mouthwashes that exacerbate symptoms.
  • Use viscous lidocaine, diphenhydramine liquid, dyclonine lozenges, or antacid suspensions to help with pain control.
  • Reduce stress.
  • Use alt-water rinses to relieve pain and keep ulcers clean.
  • Use antiseptic mouthwashes to prevent secondary infection.
  • Avoid alcohol and carbonated drinks.

Talk to an online doctor at Telegra MD to determine whether you have recurrent cold sores or canker sores and to develop a treatment plan. Prescription medications are available to treat both conditions.


While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.


1. World Health Organization. Herpes simplex virus. Accessed March 8, 2023.

2. James C, Harfouche M, Welton NJ, et al. Herpes simplex virus: global infection prevalence and incidence estimates, 2016. Bull World Health Organ. 2020;98(5):315-329. doi:10.2471/blt.19.237149

3. Opstelten W, Neven AK, Eekhof J. Treatment and prevention of herpes labialis. Can Fam Physician. Dec 2008;54(12):1683-7.

4. Baccaglini L, Lalla RV, Bruce AJ, et al. Urban legends: recurrent aphthous stomatitis. Oral Dis. Nov 2011;17(8):755-70. doi:10.1111/j.1601-0825.2011.01840.x

5.  Cui RZ, Bruce AJ, Rogers RS, 3rd. Recurrent aphthous stomatitis. Clin Dermatol. Jul-Aug 2016;34(4):475-81. doi:10.1016/j.clindermatol.2016.02.020

6. Lalla RV, Choquette LE, Feinn RS, et al. Multivitamin therapy for recurrent aphthous stomatitis: a randomized, double-masked, placebo-controlled trial. J Am Dent Assoc. Apr 2012;143(4):370-6. doi:10.14219/jada.archive.2012.0179

7.  Altenburg A, El-Haj N, Micheli C, Puttkammer M, Abdel-Naser M, Zouboulis CC. The Treatment of Chronic Recurrent Oral Aphthous Ulcers. Dtsch Arztebl International. 2014;111(40):665-673.