Consuming these can bring on an anaphylactic reaction, in which a person's throat closes, cutting off oxygen, or the stomach convulses and the lungs eventually swell up.

WSJ: Finding Food Allergy Allies

Dr. ROBERT WOOD (Johns Hopkins University): We thought that those that had had a severe anaphylactic reaction would automatically be less likely to outgrow their allergy, and that's turned out to not be the case.

NPR: Studies Predict Odds of Outgrowing Nut Allergies

For example, the doctor could create an asthmatic patient with chronic heart disease who is taking a handful of certain drugs and is currently experiencing anaphylactic shock, a severe allergic reaction.

FORBES: The Perfect Patient