The white ribbon of foam on a toothbrush may be less innocent than it looks, especially for people whose mouths repeatedly develop painful ulcers after the ordinary ritual of brushing. Foam has a cost. Sodium lauryl sulfate, or SLS, is a surfactant added to many toothpastes because it disperses debris and creates lather, yet its detergent action can disturb the epithelial barrier of the oral mucos...More