Anecdota: SLS always causes mouth sores aka canker sores for me. My inner cheeks and gums were covered in them before I figured it out. It was a very painful existence. Other people online reporting that cutting it out helped them saved me. I'm sure there are people who can tolerate SLS just fine, but I am not one of them, and the evidence has been clear cut enough for me that an inconclusive NIH study will do nothing to move the needle.

For anyone reading this suffering the same fate, benzocaine, which is commonly sold near the toothpastes, is an absolute lifesaver when you have a canker sore. It's sold under the name "Kanka" but any store brand alternatives should work just as well.