Your Stuffy Nose
Pass the tissues—and some gum, please. When a cold prevents you from breathing through your nose, you're forced to inhale and exhale through your mouth. This dries out the tissues and reduces the flow of saliva—the mouth’s built-in cleanser, which not only rinses away food particles but also neutralizes decay-causing acids and acts as a natural antiseptic to keep bacteria in check. The less saliva, the more bacteria—and the more potent the odor. An easy remedy (for your breath, if not your cold): Chewing gum—as long as it's sugarless—has been shown to increase the flow of saliva.