Hi anirudh...basically this kind of food allergies differs from person to person.
The method to identify it would be if you get any allergies after having it, it means that food is not suitable for you and its causing some problem...so avoid this variety of food or drink from next time.
Even my hubby used to get allergy after having brinjal (only if he have it outside)....so now he has stopped having brinjals outslide. Similary my FIL has allergy towards cucumber, mangai and tomato..he completly avoids it. So, it better than you avoid the food, instead of gng for unknown remedies.
You can even contact a dermatalogist, if you have these kind of skin problem after having any food.