Variety of reasons for ulcers. Better to get a detailed evaluation and blood tests to exclude causes.

Most common reason for apthous ulcers is stress Or Next time carefully observe if it is due to some specific food product or preservative could be allergy

 If you have recurring issues of mouth ulcers, the reasons may be any of the following: - Stress and anxiety in daily life Eating certain foods - such as chocolate, spicy foods, coffee, peanuts, almonds, strawberries, cheese, tomatoes or wheat flour - Toothpaste containing sodium lauryl sulphate - Stopping smoking - when you first stop smoking, you may develop mouth ulcers An allergic response to certain bacteria in your mouth Impaired immune system - Bechet's disease, that causes inflammation all over the body - Celiac Disease- an intestinal disorder caused by sensitivity to gluten a protein found in grains - Inflammatory bowel diseases like Crohn's and ulcerative colitis