Nope, sorry, life-threatening gifts are not something you are obliged to accept at all. Announce before the holiday season that because of your life-threatening allergies, you can no longer accept *any* food gifts because of the risk. Emphasize that while you appreciate the sentiment, ask that they please donate to the food bank or homeless shelter in your name instead.

If they insist on giving these gifts, *return them ASAP* with a polite reminder about your life-threatening allergies and request to donate in lieu. And do it until the gift-givers take the hint. No, this is not a polite solution, but this attitude of "but a little won't hurt you!" needs to stop. Because the next step may be that they start adding nuts or dairy secretly to your food.