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Mouth Sores: An Overlooked Cause SLS

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mouth sores

Today I’m going to talk to you a little bit about mouth sores and a possible cause that you may not be aware of. There are a lot of people that deal with mouth sores, also called canker sores, aphthous ulcers, or aphthous stomatitis. In fact, 1 in 5 people in the general population are affected by mouth sores.

What do mouth ulcers look like?

Mouth ulcers or aphthous ulcers are different from the big sores that some people get on the outside of their lips. These are actually caused by a type of herpes virus, and they can be contagious.

Aphthous ulcers or mouth sores are not contagious. They occur inside your mouth. They can be on the side of your tongue, on your gums, on your cheeks, or on the very inside of your lips. Mouth sores usually look fairly irregular. There can be one sore or multiple ones. If you’ve had them, you know exactly what I’m talking about. They can be very uncomfortable.

One thing we know is that once you get one of these little sores, they can feel much bigger than they usually are. Although some people can have mouth sores that are the size of a quarter.

What causes mouth ulcers?

Nobody exactly knows why these occur. There are various causes and sometimes it’s very frustrating not knowing what caused your mouth ulcers. It’s believed to be an immune mediated response triggered by local trauma to the area (for example, these dangerous TikTok dental trends can cause oral trauma).

Emotional or psychological stress can also cause mouth ulcers. Other possible causes of aphthous ulcers are menstruation, changes in the oral microbiome, and exposure to toxins such as nitrates in drinking water.

Trying to identify causes of mouth ulcers is important, if at all possible. One possible cause that is frequently overlooked is a common ingredient in toothpaste. It’s called SLS or sodium lauryl sulfate.

SLS is present in most commercial toothpastes and many other oral hygiene products. It’s what makes your toothpaste foam. Think of it like a soap, surfactant, or detergent. It’s the same substance that makes other cleaners foam.

Why do they put SLS in our toothpaste?

Well, first of all, SLS does give us a sense that there’s a cleaning action that takes place. Beyond that, it’s difficult to say how necessary SLS is in our toothpaste. But because it’s a surfactant, it can help with the cleaning – there is some limited evidence on that.

But there is also some decent evidence about SLS-induced mouth ulcers. Also, I’ve seen it many times in my patients, that SLS can cause mouth sores.

How does SLS cause mouth ulcers?

Sometimes, just by eliminating SLS, you will also eliminate mouth sores. It is known that SLS can, in some people, break down the surface of the tissue inside the mouth, and this is why it happens and mouth sores develop.

What’s the best treatment for mouth sores?

For some people, it’s as simple as eliminating commercial type toothpaste and choosing something that is SLS-free. You can find SLS-free toothpaste in supermarkets and pharmacies. This type of toothpaste is not going to foam as much, so there could be a sensation that it’s not cleaning as well. But most of these SLS-free toothpastes work just fine if you use them consistently with the correct brushing technique and take your time brushing your teeth as you should be doing a couple of times a day.

How long do mouth sores take to go away?

Once you get one of these, you’re probably looking at a 10- to 14-day course for it to completely heal. Oftentimes, mouth sores get worse before they get better.

Can SLS-free toothpaste make mouth sores disappear?

If you’re struggling with mouth sores and you just have never really been able to figure out what’s causing this problem, then do a trial. Eliminate the regular toothpaste that you’re using and buy one that’s SLS-free. You can find them online, like on Amazon. Make sure it’s a good one that has good reviews. Check the other ingredients as well. Toothpaste tablets may be worth considering as they contain fewer chemicals and preservatives.

Just see what happens. Give it a little bit of time. Depending on what the frequency of your mouth sores is – some people only get them once in a while, some people are dealing with them on a continuous cycle. But I would give it a good 90 days to see if you can tell a difference. Pay attention to what happens there. It could be that that’s the answer.

If not, then you might need to explore other possibilities. Some people are sensitive to spices like cinnamon, for example. I have seen patients where just the mint flavoring in their toothpaste was enough to cause irritation in their oral tissues. Not always mouth ulcers, but irritation.


Now you know one of the common causes of mouth sores, that is sodium lauryl sulfate (SLS). If you’re dealing with mouth sores, give SLS-free toothpaste a try and see if it works. At Express Dentist, we have a trusted network of dental professionals that we can connect you with. If you have more questions about mouth ulcers, or you’re dealing with mouth irritation or ulceration, anything like that, reach out to us and we can put you in contact with a top-rated dentist in your area. Feel free to give us a call, contact us, and we’ll help you get to the bottom of it. All the best to you and your oral health.

About the author

Dr Greg Grillo
Dr. Greg Grillo

Dr. Greg Grillo DDS studied at the University of Washington where he received a bachelors degree with Honors and later attended dental school on the same campus. Following school Dr. Greg served in the United States Navy as a dental officer. During this time he received advanced training in specialty areas of dentistry while also treating families of members of the military.

As well as sharing valuable information on dentistry and oral health, Dr. Greg remains a practicing dentist to this day. He works with families in the Okanogan Valley where he lives with his wife and three children.

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