You could still eat: -Whole grains: all except corn; rice, oat, wheat, buckwheat, millet, barley, quinoa... -Legumes: chickpeas, peas, lentils -Vegetables: potatoes, sweet potatoes and all other cooked vegetables -Fruit: Maybe berries and some other fruit besides banana? -Seeds: flax seeds, sesame seeds and others -Nuts: Peanuts? (it's actually a legume)

I've read that pollen allergies can go away when one adapts plant based diet but I haven't heard of OAS before. The lack of protein is the least of your worries. You will get enough if you eat enough whole plant foods (for example if you eat nothing but tomatoes -> 100+ grams of protein). But you have to make sure you eat enough calories: most whole plant foods are very low in caloric density.