There are probably some variations in the methods used for food challenges by various offices, but our allergist's procedure has been standard in the 7+ years that we've worked with him. Sophie had her first food challenge when she was 1 year old, and she had her most recent challenge a few days ago, and they were much the same.
For almost all of our food challenges, we were asked to provide the food. The exception to this was her peanut challenge, where the RN used peanut butter that she keeps at the office for those challenges. For Sophie wheat challenges, both times we were instructed to bring Cream of Wheat and some sugar to make it more palatable. When we arrived at the office, the RN prepared the Cream of Wheat. And then we began.
Dose 1: A tiny amount (approximately 1/8 tsp.) of the food was placed on Sophie's tongue. With peanuts, the RN touched the food to her tongue and then scraped it off, but with milk and wheat she was instructed to swallow it. We then watched for signs of a reaction for 10 to 15 minutes.
Dose 2: Sophie was given slightly more of the food, maybe ¼ tsp. And again, we waited to see if she would react for about 10 to 15 minutes.
Doses 3+: Each dose was larger than the previous dose. The size of the final dose depends on the food being tested. For Cream of Wheat, Sophie ate the entire bowl by the time we were done. After eating the large final amount, we waited for about 30 minutes at the office for her to react. Since she didn't, we got to go home with wheat removed from her list of allergens! The whole process takes about 2 hours.
It is vital for people with a history of serious food allergies to do their food challenges with a physician at his/her office. If Sophie had started to react at any point during the process, the RN and allergist have an abundance of medications available to treat her symptoms, as well as the requisite experience to know how she should be treated. Had there been a problem, they could have administered any combination of Benadryl, steroids, albuterol, and epinephrine, based on her symptoms. Never try a food challenge at home, even if you have medications there. Our experience with Sophie's reaction to a pecan reaffirmed this for me!