Oral food challenges are the "gold standard" of food allergy testing, yet they can still have a 10% rate of false negative results. A recent study found that waiting a day and then repeating the oral challenge reduces the rate of false negatives.
Researchers think that some people may develop a short-term tolerance to a food when they are fed tiny, and then increasing doses of the food on one day. They may have no reaction while in the doctor's office, but then try the food at home and have a reaction to it.
When these people were re-tested in the doctor's office they day after their first oral challenge, they reacted to the tested food. Most of the reactions were mild, but were enough to determine that the food was an allergy trigger.
While false negatives only occur in 1 out of 10 cases of testing, they are of serious concern to people with food allergies, who need to be certain that the food they are eating is safe for them to consume.