Mouth ulcers are painful white sores that pop up on the tongue, lips, gums and inner side of the cheek and make it difficult to eat and drink. Mouth ulcers are also called Canker Sores. Mouth ulcers occurs due to several reasons like nutritional deficiencies particularly deficiency of vitamin B and C, eating highly acidic or spicy foods, stress, poor dental hygiene and food allergies. They usually occur in clusters but sometimes one at a time and take almost 7 to 10 days to heal. Though mouth ulcers are not contagious, they tend to recur in people with weak immune systems. There are several home remedies that can bring relief from mouth ulcers.