Food challenges play an important part in food allergy diagnosis, especially in cases in which the history and allergy tests disagree with each other, or do not yet confirm the allergy. Only very few specialists and centres perform food challenges. In a food challenge, the doctor/nurse will give the child tiny, and then steadily increasing, amounts of the food in question every 15-20 minutes or so, watching the patient very very carefully for signs of a reaction.
If the patient has a reaction, the challenge is stopped, appropriate treatment given to deal with reactions, and the patient is observed for at least 2 hours to make sure they have settled completely. If the patient manages to reach the “top dose”, they are also observed for a further 2 hours to check for late reactions.