Does your research show that parents are testing their children for food allergies BEFORE actually trying to feed their children the food item? Especially for peanuts?
Good question! The problem is that many doctors, suspecting one allergy, will test for a whole battery of allergens without any clinical indication that they are warranted. Some reactivity will lead to a suggestion that the food is dangerous, or at least, better be safe than sorry. This has its absurd manifestations, such as Orthodox Jews being tested for shrimp, lobster, and pork, all foods that they will likely never eat, and be found positive. Research shows that they can test positive to shellfish because they are cross-reactive with allergens in dust mites and cockroaches, which they have inhaled, I might add, not eaten. Normally, we think of food allergies developing only after you have actually ingested the food. However, even the Orthodox can be rebellious. There’s a touching story about this in our book. A teenage boy tested positive for lobster (having eaten it naughtily with some friends) and his father the Rabbi, asked him sternly but kindly in Yiddish, “How did it taste?”
With people who have no such dietary restrictions, an equivocal finding of allergy can lead to making life more miserable than it has to be because you may decide to limit the diet unnecessarily. As to the issue of retesting, if you are using iffy tests as the baseline for your diagnosis, the results will remain iffy. Why sit around with your fingers crossed waiting for a false positive to turn to a negative?
Allergists rely on tests to a limited extent. A thorough clinical history is more important. Once I am convinced that a food allergy is real, as time goes on, I don’t routinely check to see if children are “still” positive. I take my cues from the patient. What usually transpires is that Mom will bring the child to the office and report that he ate (whatever) and nothing happened. With something like ice cream for a child who is egg or dairy allergic, the child will usually indulge himself pretty thoroughly before getting up the courage to tell Mom and Dad. That doesn’t usually happen with things like kiwi.
I will then do a modified food challenge—the gold standard double blind placebo food challenge is pretty arduous, and this is bad enough. This should only be done by an experienced allergist. It consists of applying a sample of the food to the skin, taking before and after pictures. If the first application doesn’t react, we repeat the process on the lips without letting the patient ingest it. The final stage is full ingestion, with the doctor at the ready with epinephrine. By the time we get to this stage, we are pretty sure there will be no harm.
Interestingly, even if the results are negative, both patient and parents won’t automatically incorporate the new freedom into the diet. They remain wary; having been so disciplined about eating the food, they might avoid it out of residual fear or habit, not out of necessity.
One last word. We talked about component testing briefly in the book, but we know a lot more about it now. I was one of the early adopter allergists in this country (it is common in Europe); Phadia, (now Thermo Fisher Scientific) approached me because I am visible in the New York allergy community to try its ImmunoCap tests. The FDA has dragged its feet in approving them, so reimbursement remains a problem, although approvals are now coming through. Regardless, many parents are all too happy to pay for them out of pocket—they aren’t really that expensive. Unlike old blood tests, or even skin tests, they show whether a patient is only reactive, mildly allergic, or dangerously allergic. This could supply the missing link on the question of retesting.