Mouth sores, also commonly called canker sores, can form on the cheeks, gums and insides of the lips. They are often quite painful and can interfere with eating. Canker sores have several causes, including stress, nutritional deficiencies, viral infections and biting of the cheek. Everyone experiences a mouth sore at one time or another, so knowing how to treat them is important.Consider the potential causesThe most effective way to treat recurring mouth sores is to practice prevention. If you have a chaotic life, stress may cause the sores. Managing that stress with deep breathing may help. If you have a poor diet, increasing your intake of fruits and vegetables or adding a multivitamin supplement to your routine may prevent canker sores from returning.Medications that workTo relieve the pain that mouth sores cause, you can try taking an over-the-counter NSAID, such as naproxen or ibuprofen. This does not heal mouth sores, but may help make eating more comfortable. For serious and recurring sores, doctors may prescribe a medication called Oracort that you can rub on the sores to speed healing.To avoid unnecessary pain, switch to a mouthwash that is free from sodium laureth sulfate, a substance that can aggravate canker sores and slow healing. Simple products you can applyRinsing your mouth with salt water can speed healing, though it may cause pain. You can also make a mixture of baking soda and water, and apply this to the sore with a cotton swab. Hydrogen peroxide also works well and prevents infections from developing. Some people find that drinking apple juice helps soothe the sores and promote healing.Canker sores are painful and most people experience them from time to time. Luckily, there are many effective ways to treat them, so you can get on with your life and start eating again.