-Eat nutritious food. Include vitamin B12 containing food.
-Drink at least 8-10 glass of water throughout the day.
-Try to find out if you are allergic to certain food, toothpaste or medicine.
-Use herbal toothpaste.
-Avoid oily, spicy, and junk food.
-Stop smoking, if you smoke and also alcohol.
-Drink a glass of cold milk with a teaspoon of honey in it.
Hope the above tips will help you whatsoever may be the cause.