Tomatoes and peppers are part of the vegetable family known as nightshades. Nightshades are supposed to aggrevate arthritic pain; but, there have been no definitive studies done yet. I, myself, have tried eliminating nightshade vegetables from my diet as an experiment; and, found that it made no difference that I could tell.
Other nightshades include:
•potatoes (with the exception of sweet potatoes)
•sweet and hot peppers (including paprika, cayenne pepper; and, sauces made of peppers such as Tabasco sauce)
•ground cherries (similar to a tomato)
•tomatillos and tamarillos (tomato varieties)
•garden huckleberry and naranjillas (fruits)
•pepinos and pimentos (close relatives of the tomato)