There is no sure-fire way to prevent mouth sores. Preventive measures may depend upon the specific condition or infection that a person is attempting to avoid. For example, certain antiviral medications may be able to suppress an outbreak of cold sores during periods of increased susceptibility (e.g., prior to dental treatment, intense sun exposure). This type of medication may have no effect on canker sores because they may not be caused by viruses. Some studies have shown that ice chips and certain medicated mouth rinses may help to prevent mouth sores caused by chemotherapy.

Antifungal medications have been prescribed to prevent cases of thrush (which results in skin discoloration of the mouth). However, use is controversial since the Candida fungus that causes thrush appears to develop a resistance to this type of medication, making it ineffective after an extended period of use.   

In general, there are actions people can take to avoid the most common mouth sores, including:

• Getting regular dental examinations. Periodic visits to a dentist can help identify any causes for concern in a patient’s mouth. A dentist may be able to smooth rough edges on sharp, pointed teeth that can irritate the lining of the mouth and cause mouth sores. Fixing ill-fitting dentures can also help alleviate tissue irritation in the mouth.
  
  
• Practicing good dental hygiene. Proper daily brushing and flossing can help keep the gums and teeth healthy, and help to avoid infections that may cause mouth sores.
  
  
• Avoiding potential irritants. By avoiding the products that can irritate the sensitive lining of the mouth, a person can prevent some types of mouth sores. Products to avoid include tobacco, very hot foods or beverages, alcohol, caffeine and foods that are acidic, spicy or hard and crunchy.
  
  
• Using sunscreen. Applying sunscreen to the lips may help prevent an outbreak of cold sores during periods of sun exposure.
  
  
• Maintaining good immune system health. Eating a balanced diet, drinking plenty of water, getting plenty of sleep, exercising moderately and keeping stress levels to a minimum can all help a person’s body fight infections that can lead to mouth sores. Vitamins and other nutritional supplements can also help.
  
  
• Avoiding people with contagious illnesses. Staying away from people with infectious illnesses can help prevent infections that can cause mouth sores. This includes refraining from kissing or skin contact with people who are sick – especially anyone with noticeable cold sores.
  
  
• Practicing good overall hygiene. This includes frequent hand-washing and not sharing foods, beverages, or personal belongings (e.g., lip balm, lipstick, toothbrush, razor) with others, which can spread infection that may cause mouth sores.