What causes canker sores? how can it be a reaction to stress?

all this time i thought it was lymphnode drama
someone even suggested herpes.
three prividers (i work at a health center) saw me today and immediately said they were canker sores...one even suggested they can be caused by stress..any ideas?

awesome thanks.
the doctor asked if i had any recent trauma in my mouth and i stated that i had bit myself once while chewing gum haha...it was painful...

egh there awful! i have been getting them since i was a kid. mostly i get them from very acidic fruits such as oranges. i knew i was asking for it when i ate them lol...but as far as stress goes u can get them from that too its the acid from ur stomach the glands in ur mouth will swell up at first usually and then there is one..they can be on ur tongue on ur gums and they hurt like a son of a gun....it takes time for them to go away the only pain reliever i use is a medicine called Ziactin it burns so bad when it goes on but it puts like a protective coat on it and numbs it....salt water burns like fire but helps sometimes too....ne thing acidic will cause them. and unfortunately because of them i hate ne thing orange flavored cause immediately i associate the flavor with a painful canker sore....
sucks that u get them but there isnt a cure sorry...

The exact cause of most canker sores is unknown. Stress or tissue injury is thought to be the cause of simple canker sores. Certain foods 鈥?including citrus or acidic fruits and vegetables (such as lemons, oranges, pineapples, apples, figs, tomatoes, strawberries) 鈥?can trigger a canker sore or make the problem worse. Sometimes a sharp tooth surface or dental appliance, such as braces or ill-fitting dentures, might also trigger canker sores.

Some cases of complex canker sores are caused by an underlying health condition, such as an impaired immune system; nutritional problems, such as vitamin B-12, zinc, folic acid, or iron deficiency; and gastrointestinal tract disease, such as Celiac disease and Crohn's disease.

herpes 1 as opposed to Herpes simplex II (which is the same virus but when spread to the genitalia) the only way stress affects an outbreak is if you already are infected with this disease then under stress you will have break-outs more often this is true DO NOT PARTICIPATE IN ORAL SEX WHILE YOU HAVE A SORE or you will give your partner HERPES SIMPLEX II

It can be herpes, or it can be bitting the skin and it turns into a cold sore or infected white thing in your mouth. But herpes 1 is caused by stressed well outbreaked.

whats canker...(cancer??)