Eight things cause about 90% of food allergy reactions:
Milk (mostly in children)
Eggs
Peanuts
Tree nuts, like walnuts, almonds, pine nuts, brazil nuts, and pecans
Soy
Wheat and other grains with gluten, including barley, rye, and oats
Fish (mostly in adults)
Shellfish (mostly in adults)
Almost any food can trigger an allergy, though. Less common ones include:
Corn
Gelatin
Meat --
beef,
chicken, mutton, and pork
Seeds, often sesame, sunflower, and poppy
Spices, such as caraway, coriander, garlic, and mustard.
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Brinjal (Eggplant) is related to tomatoes, peppers, white potatoes, tomatillos, goji berries, pepper seasonings. I would be on the lookout for possible allergic reaction to these related plants. I am not too sure why your body has decided to view eggplant as hostile. It is in the nightshade family maybe some protein from it ended up in his bloodstream accidentally and since then it has been tagged as dangerous and hostile.
Eggplant also contains a chemical called salicylate, which is an ingredient in aspirin. This means people with an aspirin allergy or salicylate sensitivity may also be more likely to develop an eggplant allergy or intolerance to too much salicylate.
The salicylate in eggplants may be responsible for the allergy or intolerance symptoms in some people. These people may need to avoid other foods where this chemical occurs naturally.