Canker Sores vs. Cold Sores

Gentle Dental

Young woman with cold sore looking in mirror at home

Often confused for one another, cold sores and canker sores are actually quite different. Here’s a guide to help you understand these common oral ailments.

What are Cold Sores?

Commonly called fever blisters, cold sores are caused by the herpes simplex virus (HSV-1). They typically appear as small, fluid-filled blisters on or around the lips, and are often clustered together in patches. Once the blisters break, a crust develops over the core. In most cases, cold sores heal on their own in about two to four weeks.

Spread by person-to-person contact, cold sores are usually contracted through kissing. While herpes simplex virus (HSV-1) is related to genital herpes (HSV-2), they are not the same thing. That said, both viruses can impact the genitals and mouth and can be spread via oral sex. Unfortunately, cold sores are contagious, even when no sores are apparent. This is why they are so prevalent among humans.

What are Canker Sores?

Also known as aphthous ulcers, canker sores are tiny, shallow lesions that can form on the base of the gums or the soft tissues within the mouth. Unlike cold sores, canker sores do not form on the surfaces of lips. They are also not contagious and usually go away after about a week or two. That said, they can cause pain, while making it difficult for a person to eat and talk.

Canker sores can be caused by a variety of things, including spicy and acidic foods, an injury to the mouth, stress, hormonal changes, vitamin deficiencies or autoimmune disorders. In most cases, canker sores heal up on their own; however, you should consult your local dentist if your canker sore is especially painful or large. You should also seek an evaluation if your canker sore doesn’t go away after two or three weeks.

How to Tell the Difference Between Canker Sores and Cold Sores

Size, shape and location can usually help differentiate cold sores from canker sores. If the sore appears on the surface of the lip or exterior of the mouth, it is most likely a cold sore. If the sore is filled with fluid or exists among clusters of other blisters, it is also likely a cold sore. On the other hand, canker sores will usually appear within the mouth as open sores with bright red borders and gray, yellow or white centers.

How to Get Rid of a Cold Sore

Cold sores usually clear up in two to four weeks without any treatment; however, there are prescription antiviral creams and pills that can speed the healing process. Some of the more common cold sore treatments include:

  • Famciclovir (Famvir)
  • Penciclovir (Denavir)
  • Acyclovir (Xerese, Zovirax)
  • Valacyclovir (Valtrex)

Docosanol (Abreva) is an over-the-counter cream that may also shorten a cold sore outbreak for a few hours or day if applied frequently.

How to Get Rid of a Canker Sore

Most minor canker sores require no treatment. That said, large or persistent canker sores often require medical care. Over-the-counter and prescription creams, pastes, gels or liquids may be used to help speed healing and relieve pain. Your dentist may also prescribe a mouth rinse that contains lidocaine and the steroid dexamethasone.

When patients do not respond to topical canker sore treatments, they sometimes require oral steroids or alternative medications. In severe instances, a canker sore may have to be cauterized to close the wound and promote healing.

When to Seek Help for Canker Sores and Cold Sores

While canker sores and cold sores typically get better without the need for medical intervention, they can lead to bacterial infections and other complications in some situations. If you experience any of the following, make an appointment to see your dentist or doctor:

  • A fever
  • Intense or lingering pain
  • Sores accompanied by eye discomfort
  • Unusually large sores
  • Persistent sores
  • Recurring sores
  • Difficulty breathing or swallowing

You should also see a dentist or doctor if sores appear to be spreading, or if you have an existing health issue that may weaken your immune system. Since people sometimes confuse oral cancers for canker sores, it’s also important to see your dentist if you notice any irregularities, or if a sore won’t heal on its own.