Are Canker Sores contagious? –
If you suffer from aphthous ulcers (canker sores), something that may be at the top of your list of concerns is if they are contagious or not. After all, no one wants to spread their problems to others. Especially those they are closest to.
Are canker sores contagious?
The good news is they are not. They can’t be spread through direct contact (like when kissing or accidentally touching someone’s sores), or even through the transfer of saliva (like when sharing food, a beverage, or a straw, fork, or spoon).
Bottom line, there’s nothing to be concerned about. What’s yours is yours and you don’t have to worry about passing your canker sores to other people. This condition is not contagious.
▲ Section references – NIH.gov, MedlinePlus.gov
That’s different from some other types of mouth sores.
If you mistakenly thought that they were contagious, you may be confusing your canker ulcerations with some other type of oral lesion, like cold sores, which can be spread from one person to another.
And since these two types of mouth sores are confused by so many people, we’ve created a page that provides instructions that describe how to distinguish between the two. You can find it here: Canker sores vs. Cold sores – How to tell them apart.
The next section of this page briefly discusses the science of canker sore formation and why these lesions are not contagious. And then following that, we answer some very specific questions people frequently have about being able to spread canker sores. Jump ahead.
The biology of canker sore formation explains why they’re not contagious.
It’s easy to understand why aphthous ulcers aren’t contagious, once you know a few of the details about how and why they form.
Many disease processes are initiated by infective agents (like bacteria or viruses). And if the agent is passed from an infected person to someone else, that second person is at risk for developing the same disease process.
In cases where it’s possible for the active infective agent to be transmitted from one person to another successfully, the disease is considered contagious. The method of transmission may be direct (like touching a sore) or via infected bodily discharges or fluids (like respiratory droplets or saliva). The potential for transmission may vary as the disease process waxes or wanes.
Cold sores are an example of a contagious disease process. These lesions are caused by an infective agent (a virus) and it can be spread from one person to another.
The method of spread can be direct contact with a person’s lesion (touching, kissing, etc…) or via their body fluids (like saliva). The potential for transmission varies throughout the lifespan of a person’s lesion(s) due to the varying levels of virus particles that it sheds during different stages of formation and healing.
Aphthous ulcers (Canker sores) are not contagious.
Direct or indirect contact with a lesion will not spread it.
How canker sores differ and why they are not contagious.
Canker ulcerations are caused by a person’s immune system response.
The formation of canker sores is triggered by a specific form of immune system response to the presence of chemical compounds (molecules) referred to as “antigens.” (We explain the whole process here: The biology of Canker Sore formation. )
So, as opposed to a contagious disease model where a sore is teaming with the reproducing microbes that have caused it and can be spread, … the “invading” agent that initiates canker sore formation is (often commonplace) antigen molecules that have found their way into oral skin tissue that have been (somewhat mistakenly or over aggressively) identified as being “foreign” by the person’s own immune system.
In a nutshell, canker sores are “self-inflicted.” They’re triggered by a person’s own immune system’s (inaccurate or overly aggressive) response to the presence of (often commonplace) antigen molecules. And the kind of antigen that has triggered canker sores in one person will not necessarily trigger them in another.
And, also, this point.
We’ll also mention that many of the chemical compounds thought to act as the triggering antigen for canker sore formation (medicines, compounds in foods, toothpaste ingredients, etc… Canker sore outbreak triggers.) aren’t really items that are held in the mouth long enough or in sores in quantity enough that they could be passed to others in a meaningful way.
That’s different than with a contagious disease model where at times a mouth sore may be teaming with reproducing microbes that can be easily spread to others.
… and that’s why canker sores are not contagious.
Answers to questions people frequently have about spreading canker sores.
While this section is fairly redundant, here are answers to specific questions people frequently have about the subject of spreading canker sores and how contagious they are.
Can you pass canker sores to someone else?
No, aphthous ulcers are caused by a person’s own unique immune system response to a triggering agent or event. There is no infectious or causative agent in your sores to spread.
How long is a canker sore contagious?
They’re not contagious at all. So, from the moment when you first suspect that an outbreak is coming on until the end when your last sore has finally healed, there are no special precautions to take. You can’t pass canker sores on to others.
Can canker sores be passed to a baby?
No, canker sores are not contagious and you cannot pass yours on to a child or newborn.
It is true that aphthous ulcer susceptibility may follow family lines. But that has to do with genetic factors and resulting predispositions and not the situation where you have directly spread your sores to your offspring.
Can you spread canker sores by drinking from the same cup as someone who has lesions?
No, canker sores cannot be spread by sharing food or beverages or the utensils that are used to consume them (fork, spoon, straw, glass, etc…) with someone suffering from a current outbreak.
It is true that some foods and beverages are known triggers for aphthous ulcers for some people. And sharing one of these items may trigger sores for you. But if you do then have an outbreak, it was not passed from the other individual but instead triggered by the food item you ate or drank.
Can you kiss someone with a canker sore?
Yes, there are no special concerns with doing so. Aphthous ulcers are not contagious and therefore can’t be spread by kissing or otherwise coming into contact with another person’s lesions or saliva.
Is it OK to share a toothbrush with someone who has a canker sore?
Yes, there’s no fear of spread from shared toothbrush use. (Although, in general, the idea of sharing toothbrushes isn’t usually considered a “best practice.”)
It is true that sodium lauryl sulfate (SLS), a compound frequently found in toothpaste formulations, can be a trigger for canker sores for some people. So if you’re using toothpaste on the shared brush, or if it hasn’t been rinsed off effectively, you’ll have some level of SLS exposure. But if you do experience a breakout, you didn’t “get” your sores from the other person.
Are canker sores from an STD?
No. However, people who have some medical conditions, including those that can be spread sexually like AIDS, may experience difficulties with canker sore outbreaks.
Think in terms that the medical condition doesn’t specifically cause canker sores but sets conditions within your body where you are more likely to suffer from them.
Can you spread canker sores via oral sex?
No, aphthous ulcers are not contagious, and therefore (like with kissing) having contact with another person’s sores or saliva does not pass the condition on to you.
Are canker sores contagious through makeup?
No, aphthous ulcers are not contagious, and therefore sharing or touching someone’s makeup who does have lesions is of no concern. Their condition cannot be spread to you.
In comparison, cold sores, which form on a person’s lips or surrounding face, are highly contagious and may be spread through the use of shared cosmetics (especially lipstick or lip balm).
Page references sources:
InformedHealth.org (nih.gov) – Canker sores (mouth ulcers): Overview.
MedlinePlus.gov – Health Topics > Canker Sores.
All reference sources for topic Dental Crowns.