I have joint pain that I know is a reaction to the foods I eat.  Nightshades, tomatoes, potatoes, eggplant, etc., do cause the worst problems.  I was tested for each of these foods and was allergic to each of them.  But, other foods cause the joint pain and swelling also. Garlic, wheat, and black pepper are big offenders. Watermelon also causes the same reaction.  But, if I stay away from all the foods I am allergic to, I am so much better.  Staying on a diet of fresh fruits, vegetables, and small amounts of fish, chicken and beef that I am not allergic to is difficult.   But, I've reached a point where the pain is so severe when I cheat, it isn't worth cheating. Good luck to you.  Try a very strict diet avoiding the foods you have tested positive to and I think you will be amazed at the difference.