I don't know how common an allergy to sunflower seed oil is.
It's definitely the case that food allergies can be dangerous even if the amount of food is very small. The most severe type of food allergy is generally to peanuts, and there even a minute amount of peanut products can kill a person. But peanuts aren't closely related to sunflowers at all, so I don't know if sunflower products ever cause such severe allergies.
Also, the really dangerous food allergies are generally those that cause asthma-type symptoms -- the respiratory track swells up and the person can't breathe. Luckily, you don't seem to have those sorts of symptoms. For people who do have breathing problems if they accidentaly eat an allergy-producing food, there are these "epi-pens" that a doctor can prescribe. An Epi-pen is an injector containing epinephrine (that is, adrenalin) that the person or a friend can inject to treat the airway swelling.
If you haven't seen an allergy specialist yet, that is definitely something I'd suggest. They can help you determine how severe the allergy is, and they may be able to give you treatments that desensitize you to the allergy-producing substance.
Also, I find that brands of "natural" foods are more likely than the major commercial brands to actually list the specific type of oil on their label, rather than just saying "vegetable oil." Health food brands are also more likely to use oils with specific health benefits, such as canola, rather than just whatever was cheapest at the time.
and I REALLY miss 'em....
