By Dr. Paul Ehrlich
As our millions of followers know, Dr. Chiaramonte and I are very particular about how we use allergy tests. Physicians who rely solely on tests to diagnose an allergy without a proper history or specialized clinical experience are going to end up with a lot of false positives and treatment that is wrong and expensive. This is particularly important with food allergies because it affects diet. Avoiding too many foods can lead to malnutrition.
As we say in our book: “The science shows us that skin tests and blood tests don’t really measure the same things. The antibodies that register in a blood test have a half-life of two days. They come and go without putting your immune system on a state of red alert. The ones that react in the skin have a half-life of six to eight weeks, which means that your body is ready to strike for a protracted period.”
The new NIAID food allergy guidelines call for abandoning the old blood tests—called RAST (radioallergosorbent test) in favor of “sensitive fluorescence enzyme-labeled assays” which measure allergy at the molecular level. I use these, and they are a great step forward, but it’s still no substitute for my own clinical judgment as an allergist. Among other things, they can help tell whether a patient is dangerously allergic to, say, peanuts, or mildly so.
But that’s not why I’m writing this. When new patients bring us previous test results, we often find ourselves fighting not the last war, but the one before that. For example, one “alternative” practitioner recently came to our attention for warning about allergy to caffeine, which is not an allergen, as I have written previously. What does he use to support his allergy diagnoses? A test called ELISA. I couldn’t believe it. This test is the poster child for false positives. It may indicate reactivity by revealing IgG—the good antibody—but it doesn’t reliably show allergy.
However, my surprise was mild compared to what I felt when presented with results for something called AllerTest, which is marketed along with nutritional supplements by something called the Trump Network—yes, that Trump. Far be it from me to disparage these tests without knowing more about them, and that is the point. There is no evidence I can find how they work, or if they work at all, not even on their website, let alone the medical literature. Absent evidence, as a doctor, I can only recommend that the Trump empire stick to real estate development. As a New Yorker, that’s a hard line to write. Suffice it to say, I went back to the drawing board with this patient.