Will a folic acid deficiency cause canker sores?

It can: Folic acid/folate deficiency can cause canker sores, red painful tongue, irritation/cracking at the corners of the mouth, and a type of anemia. One of the main sources of Folic Acid in the diet is from green leafy vegetables. Folic acid deficiency severe enough to cause symptoms generally requires a very poor diet, alcohol use, or is a side effect of medications like Phenytoin or methotrexate.

Possibly: It can be one of a number of contributing factors. Either consume foods high in Folic Acid or see your physician to help you determine if you are low.