What could cause me to have seven mouth ulcers?

Viral outbreak: It could be a viral outbreak such as herpes. Possibly a reaction to a new food, usually citrus. Possibly a severe vitamin deficiency, usually the b complex. . If it doesn't dissipate within 2 weeks, see a dentist or physician for a diagnosis.

Multifactorial: It's hard to pin down the exact cause of mouth ulcers or aphthous ulcers. Acidic food and drink, physical trauma to the oral mucosa, stress, side effects of medication, and autoimmune disorders are just a few of the suspected causes. Do you have other symptoms other than just mouth ulcers? Please see the dentist and md to determine the cause. Avoid acidic food/drink and rinse with warm salt water.