Mouth ulcer :
Mouth ulcers are red, yellow, or white sores that develop inside the mouth. Mouth ulcers are usually seen on the gums, tongue, roof of the mouth, inner cheeks, and inner lips of the mouth. Mouth ulcers are of different types, such as aphthous ulcers, oral lichen planus, leukoplakia, erythroplakia, oral thrush, and mouth cancer. These ulcers are usually white, yellow, or grayish in the center and red around the edges. The signs of mouth ulcers include swelling around the ulcers, increased soreness while brushing the teeth, and pain that worsens while eating spicy, salty, or sour foods. Mouth ulcers are caused by minor tissue injury from dental work, accidentally biting the cheek or tongue, allergic reaction to some bacteria, wearing braces or retainers, using harsh or abrasive toothpaste, hormonal changes during periods, stress and lack of sleep. Certain medical conditions also contribute to mouth ulcers like vitamin deficiencies, viral, bacterial or fungal infections, Crohn's disease, celiac disease, reactive arthritis, lupus and Behcet's disease.