Studies suggest that several combined factors cause mouth sores, according to Mayo Clinic. Injuries to the mouth, stress, not getting enough nutrients and food sensitivities are all common causes.
Minor injuries to the mouth occur due to biting, brushing teeth too hard, eating particularly spicy food and drinking beverages that are too hot. Using toothpastes containing sodium lauryl sulfate causes mouth sores. Sensitivities to coffee, eggs, nuts, cheese and very acidic foods also cause mouth sores, explains Mayo Clinic. Not getting enough of certain nutrients can lead to mouth sores, including vitamin B-6, vitamin B-12, zinc and folate. Hormonal changes during periods and emotional stress can also predispose a person to mouth sores. Some individuals are more likely to suffer from sores due to underlying conditions. Celiac disease, Crohn's disease, Behcet's disease, HIV/AIDS and a faulty immune system increase the risk of sores.
Avoiding foods that irritate the mouth, such as those containing a lot of acid or spice, can reduce the risk of sores. In addition, not brushing teeth too vigorously and avoiding gum chewing prevents them, advises WebMD. Certain sores should prompt a visit to a dentist or doctor. This includes large sores, intolerable pain, sores that spread and those that last for more than three weeks.