Thus, SLS is believed to increase the incidence of recurrent aphthous ulcers [2, 12, 13] by disintegration of the mucin layer, denaturation of proteins in the epithelial cells, solubilization of structural lipids of the cells and, finally, penetration of SLS into deeper layers of the mucosa where functions of the living tissue may be compromised [2]. Here, MUC5AC is linked to canker sore.