I have a couple of suggestions for you.
First, in a corn chip you would have to include any of the ingredients used directly by the manufacturer, and any product used by the suppliers in the raw ingredients. For example: when you eat chips that have been fried in oil, not only do you worry about the corn or potato allergy, but you have to include as potential allergens the oil (type of oil, or oils if it is a blend.) the ingredients used to process the oil (preservatives so it won't go rancid in the bag, and any type of chemical used to process the raw oil). You also need to consider the spices and flavorings used to give it the flavor that you like. I have found that manufacturers include only the ingredients they add directly to the product, and not necesarily the ingredients used by the suppliers. Picture this, if you are allergic to peanuts and somebody in on the suppliers side cook, fries, or adds peanut oil to thier raw materials to process into the product they sell to the chip manufacturer, you could get the impact from the oil and not know what it was because it would not be disclosed in the ingredients.
Another way to find out would be to go on an eliminaion diet. This would give you a frame work to start finding out what ingredient is that bothers you. It takes will power and organization. I once read a book called "Arthritis the allergy connection" It may not be in print now. But, it did have a wonderful insight into the elimination diet and some of the things this particular doctor/author, has found during his career to produce dangerous allergies.
The third way I can suggest is to go to a doctor that specializes in allergies and take the tests that determine all the things you are allergic to. It takes a while and it does cost some money (lots) and when you finally find out what it is that bothers you, you need to remember that your allergis will change as you change your lifestyle and as you get older and exposed to more or less of the allergens and new allergens.
Remember, if you have a life threatening, or severe, allergy you need to check with your doctor before you start any program that might put you at a higher risk, or place in a a position in which you will have an allegic episode, and are not prepared to cope with the results of such allergy.
Hope your sleuthing proves productive.