What could cause a sudden incidence of canker sores on the inside of mouth and lips? Theyre not cold sores and I haven't had sex recently to contract HIV or anything. I never get them now I have 4-5 sore persistent ones all at once. I also eat good.

No sure answer. There is no sure answer to this question. Stress has been associated with canker sores. Some have suspected that this may be from strep mutans- an organism found normally in the mouth and considered responsible for dental caries. Have you had your teeth cleaned at least twice yearly, flossed daily, and brushed thoroughly at least 2x daily? Good dental hygiene may help.
Canker Sores. are the most common oral lesions. Individual ulcers typically last 1-2 weeks. The cause is not known. The aphthous ulcers are usually self-limiting. Try to keep adequate oral hygiene as possible.
Unsure. Many possible causes, but the most common theme is stress. Being run down, poor sleep, poor nutrition, overall stress increase. Also, some people have reaction to foods, such as chocolate and beer. Exposure to sun will set this off in some patients. Any new toothpaste,mouthwash, foods, spices ?? Can be peculiar to the individual. Warm salt water rinses 4-5xday seem to help. Good Luck.