I keep having canker sores while my immune system is good. what other than a weakened immune system can cause this?

Canker sores: Most people who develop canker sores do not suffer from a compromised immune system. Stress and local irritation are often the cause.

Spicy foods.: Most people will get a canker sore at some point during life... It is normal, an inconvenience, but normal. One of the most common canker sore cause is spicy or acidic food: spaghetti sauce, orange juice, salsa. Canker sores become concerning only if the same one persists greater than 2 weeks.

Different causes: Intolerance of certain foods, vitamin deficiencies, dental conditions and stress are some factors but the exact cause is not really certain.