The phenomenon referred as a "sour taste in mouth" is an elusive entity about which a lot can be said, but very little that is conclusive. To sum it up, theories and sufferers propose that it can be causes by foods (obviously), periodontal disease, underlying disease, vitamin deficiencies, neurological disorders, drugs, dry mouth, and even pregnancy. If you have a persistent problem try to work your way through it by considering your own particular circumstances. Food and pregnancy are easy to rule out - if either of these could be the cause, it will probably pass.

Are you taking any drugs regularly? Many drugs have mild to severe side effects including sour taste in mouth. If possible, discontinue the drug or replace it with another alternative and wait to see if the taste problem clears up. if you can't discontinue or change the drug, you may have to resort to using an oral rinse or mouthwash on a regular basis to keep the problem at a manageable level. If you suspect that the drug is causing dry mouth or gum disease, you may be able to resolve the taste problem by treating the underlying one.