Man touching mouth in pain

Sodium lauryl sulfate and mouth ulcers: is your toothpaste to blame?

That crater-like bump you can get on the inside of your lip, cheeks, and on your tongue is called a mouth ulcer or canker sore. Toothpaste containing sodium lauryl sulfate has been linked to the recurrence of these open sores inside the mouth. What’s the story?

Here, we’ll explore the toothpaste ingredient that could be a possible cause of mouth ulcers according to some studies1. We’ll also introduce a type of gentle toothpaste for mouth ulcers that can be beneficial.  

What is Sodium lauryl sulfate (SLS)?

Sodium lauryl sulfate (SLS) is a surfactant (foaming agent) used in the beauty and personal care industry to help with cleaning. Originally developed in the 1930s, it’s now found in all sorts of products, from shampoos to toothpastes.

Can SLS cause mouth ulcers?

Sodium lauryl sulfate is a safe ingredient, and many people enjoy that foaming sensation when cleaning their teeth. However, some people are more prone to irritation to SLS than others. This is especially the case for those with particularly delicate oral tissues, and those who regularly experience mouth ulcers. While SLS does not cause mouth ulcers, it can cause further irritation.

Why is there an ingredient in toothpaste than can cause mouth sores?

Surfactants create foam that helps loosen debris, which makes it easier to brush your teeth. SLS is a widely used foaming agent that most people are fine with, hence why it’s commonly included in most toothpastes.

However, research carried out by the British Dental Journal and the US National Center for Biotechnology Information (NCBI) has shown that sodium lauryl sulfate could be an irritant to some mouths and even damage the oral mucosa’s delicate layers. That’s why some people prefer toothpastes that don’t contain SLS3,4.

Patients with a delicate oral mucosa are more likely to find SLS containing toothpastes less suitable.
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Dentist Surina Seghal

Reasons you get a canker sore: toothpaste is not the only cause

It’s important to note that although there are studies that have found an increase in the chance of getting a recurrent canker sore from toothpaste that contains sodium lauryl sulfate, mouth ulcers can also be caused by other factors. Possible causes include:

  • Stress
  • Hormones (changes during pregnancy or menstruation)
  • Biting your cheek or tongue
  • Poorly fitting braces or dentures causing irritation
  • Bacteria imbalance in the oral microbiome weakening your mouth’s natural defences
  • Certain foods (particularly spicy food, acidic food, and very hot food)

Underlying health conditions and certain medicines and medical treatments can also be reasons for recurrent canker sores. If your mouth ulcers keep coming back, last for more than three weeks, are very painful or turn red, consult your dentist for advice.

SLS-free toothpaste for mouth ulcers

Two Zendium Toothpaste Tubes

Looking for toothpaste suitable for people suffer from mouth sores? If you suffer from recurrent mouth ulcers then you might want to try SLS free toothpaste. Canker sores can benefit from mild toothpastes, particularly sensitive formulations like Zendium Classic Toothpaste. It’s free from SLS and is formulated for people with tooth sensitivity and vulnerable mouths, including those with ulcers and delicate gums. It contains natural antibacterial enzymes and proteins to gently work in harmony with your oral microbiome, boosting your mouth’s natural defences.


1,2 Herlofson BB. Barkvoll P. Sodium lauryl sulfate and recurrent aphthous ulcers. A preliminary study. Acta Odontol Scand 1994: 52: 257-259.

J Microsc Ultrastruct. 2020 Apr-Jun; 8(2): 80.

4 Hassona, Y., Scully, C. Oral mucosal peeling. Br Dent J 214, 374 (2013).

The advice in this article does not constitute medical advice; it is solely available for information purposes. We recommend that you consult your dentist if you are experiencing any tooth or gum problems.