Trying to diet with severe food allergies

I am trying to figure out how to start a diet to lose weight. I am very overweight and I keep gaining weight due to the fact that my allergies are out of control and my dose of daily prednisone has been increased yet again. I try to work out most days. I've given up soda, except for the occasional treat one. I've cut back on fast food. This doesn't seem to have done much. Now I'm seriously looking into diets. The main problem with most diets is the fruit and vegetable part. I am highly allergic to most fruits and vegetables. These allergies are so bad that even touching or smelling certain ones can send me to the ER. And I recently found out I have minor nut allergies. What am I supposed to do?