Bring as much information to the allergist appointment as you can about the food you believe caused the reaction. What were the ingredients, how much was eaten, and what else was being eaten at the time? Your allergist will also ask about the reaction itself: What were the symptoms, how long after the food was eaten did they start, and when did they subside?
Allergies are often genetic, so your allergist will want to know whether anyone else in the family has allergies and what they are allergic to, including other issues, like hay fever.
The allergist will perform testing to confirm what your kid is allergic to. Unfortunately, the two most common types—skin-prick tests and blood tests—don’t give a definitive answer on their own. “That’s why a child’s historical reaction to the food is important,” says Julia Upton, an allergist at Sick Kids Hospital in Toronto. She stresses that allergists should only test for foods they suspect might be a problem. That’s because the tests only show if your child creates IgE antibodies to the food, but often the body can create the antibodies even when you don’t have an allergic reaction. When a person tests positive to a food but isn’t actually allergic, they may unnecessarily avoid that food. Because skin-prick and blood tests aren’t reliably diagnostic, an allergist may suggest an oral food challenge, in which your child actually eats the suspect food under medical supervision to see if there is a reaction.
Based on the information you’ve shared and the testing, your allergist will make a diagnosis and tell you what foods you’ll need to avoid. Some families find they leave the appointment with more questions than answers, says Beatrice Povolo, a spokesperson for Food Allergy Canada. It can be helpful to do your own research or join a local food allergy support group to help you navigate this new reality.