Studies have shown that SLS (Sodium Laurel Sulfate) can be a factor in incidences of RAU (recurrent aphthous stomatitis), or canker sores. SLS is a foaming agent commonly found in toothpaste. Below are abstracts from 2 studies. The second study only included 10 patients, which is a very low sample size, but many canker sore sufferers have reported a decrease in frequency after switching to a low SLS brand.
dentrifice = toothpaste
Chahine, L., Nancy, S. and C. Wagoner THE EFFECT OF SODIUM LAURYL SULFATE ON RECURRENT APHTHOUS ULCERS: A CLINICAL STUDY, Compendium 1997; 18(12) pgs 1238-1240
Abstract: This study measured the incidence of recurrent aphthous ulcers during the use of dentrifices with and without sodium lauryl sulfate (SLS). A single-blind crossover design was used. A statistically significant reduction in the recurrent aphthous ulcers was observed during 2 months’ use of SLS-free dentrifice compared to to 2 months’ use of SLS-containing dentrifice. These results support the results of an earlier independent study, and suggest that use of an SLS-free dentrifice should be considered for individuals suffering from recurrent aphthous ulcers.
Herlofson, B.B. and P. Barkvoll SODIUM LAURYL SULFATE AND RECURRENT APHTHOUS ULCERS: A PRELIMINARY STUDY Acta Odontol Scand 1994; 52 pgs. 257-259
Abstract: Sodium lauryl sulfate (SLS), a synthetic detergent commonly used in dentrifices, is an effective denaturant. The aim of the present study was to investigate the effect of SLS in patients with recurrent aphthous ulcers (RAU). Ten patients with multiple minor RAU participated in the study. The mean incidence of RAU was 17.8 during a 3-month period before the study. The patients used a dentrifice containing 1.2% SLS for a test period of 3 months followed by a dentrifice without SLS for the same time period. The results showed a statistically significant decrease in the number of aphthous ulcers from 14.3 after using SLS-containing dentrifice to 5.1 ulcers after brushing with the SLS-free dentrifice (p<0.05). It is suggested that the denaturing effect of SLS on the oral mucin layer, with exposure of the underlying epithelium, induces an increased incidence of RAU.