Apthous ulcer, also known as canker sore, are small and shallow lesions that develop in the mouth or at the base of the gums. They can be painful and can make talking and eating difficult. They can be small, oval shaped with red edges or large and deeper with irregular edges and extremely painful. Most canker sores go away on their own in a week or two. However, if they dont heal, are large, recurring, painful with fever, then one should visit the doctor. The possible triggers for the development of apthous ulcers may be a minor injury because of some dental work, overzealous brushing, injury, toothpastes and mouth rinses containing sodium lauryl sulfate, a diet lacking in vitamin B- 12, zinc, folate (folic acid) or iron, hormonal shifts, stress, or as a result of few diseases like celiac disease, inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis, Behcet's disease, HIV/AIDS, which suppresses the immune system. Diagnosis is done from case history and physical examination. Various treatment options like mouth rinses, topical creams, oral steroid medications, nutritional supplements can be given. Various dietary and lifestyle choice may help in reducing the severity and frequency of developing ulcers and also for preventing. They are eating healthy foods to help prevent nutritional deficiencies, follow good oral hygiene habits, remove sharp edges of teeth or braces, reduce the stress. Recurring mouth ulcers can be effectively treated by homeopathy. Commonly used homoeopathic remedies for aphthous ulcers are Borax, Sulphuricum acidum, Kali muritacum, Mercurius solibilis, Arsenicum album.