False positive allergen test: Don’t scare yourself into getting sick

Let me give you some reassurance: "Positive" on the allergen test report definitely does not mean that you are really allergic to the substance. The current false positive rate of clinical statistics is generally above 30%, and the false positive rate of some non-standard tests can even exceed 80%. There is no need to be frightened when you see the plus sign and put the corresponding food on the blacklist, or even blindly avoid it for a long time. In the end, you are not affected by the allergy, and you scare yourself out of malnutrition.

Last week, when I was helping my tutor organize follow-up files in the allergy department, I met a mother who was so anxious that she was crying. She was holding a 20-item food allergen test sheet made by a private institution. The three items on it were strong positive for eggs, milk, and wheat. She said that she had cut off these three types of food for her 3-year-old daughter for almost half a year. She recently had a physical examination. Her height was 2 centimeters shorter than the standard for her age, and she often caught colds. As a result, we did an oral provocation test. The baby drank a whole box of warm milk and ate half a boiled egg. After observing for an entire afternoon, there was no allergic reaction. It was a pure false positive. The mother regretted it so much that she said she would not have blindly believed in the list if she had known better.

Many people think that the results of testing instruments are certain, but this is not the case. Allergen testing is originally an auxiliary diagnostic tool, and it has many limitations. Take the most commonly used serum-specific IgE test, for example. It checks whether you have antibodies against a certain type of allergen in your body. However, if you have antibodies, you will be allergic. Many people have been exposed to such substances before, and their bodies have produced antibodies but have developed immune tolerance. They usually do not have any allergic reactions at all. In this case, a positive test is actually "fake." I have seen many people who have been found to have high dust mite IgE, but they usually neither sneeze nor rub their eyes, which does not affect their lives at all, and there is no need to undergo desensitization treatment.

There is also the "food intolerance test" that many institutions are boasting about, but it actually checks for specific IgG. This project is very controversial in the industry: the Allergy Branch of the Chinese Medical Association has long issued a statement, clearly stating that the IgG test results are not clearly related to food allergy and are not recommended as the basis for allergy diagnosis.； However, some clinicians in the Department of Gastroenterology and Dermatology believe that for some patients with long-term diarrhea and chronic urticaria who cannot find the cause, this result can be used as a reference for dietary adjustment, but they must not be completely tabooed directly based on the positive result, let alone equated with "allergy."

In addition to the limitations of the test itself, irregular operations can also produce a lot of false positive results. For example, in a skin prick test, if you have skin scratching, or are experiencing acute urticaria, and your skin is already red when touched, then no matter what allergen is pricked, there will be a red and swollen reaction, and the results will all be positive, which has no reference value at all. Many institutions will not ask you about your recent skin condition or whether you have taken anti-allergic medicine before doing the test.

What’s even more outrageous is the bioresonance test that claims “no need to draw blood or need needles, just hold a metal rod and check hundreds of allergens in 10 minutes.” It has been counterfeited countless times by the industry and has no scientific basis at all. I met a young man before who was doing health care. This kind of test conducted by the institution was found to be positive for rice, pork, and cabbage. He himself was very happy, saying, "I have lived for 28 years eating these every day, and I have never been to the hospital." The false positive rate of this kind of test is basically more than 80%, and it is purely an IQ tax.

Many people’s first reaction after receiving a positive result is “I will never eat it again.” This is really not necessary. You first recall, do you feel uncomfortable when you eat or come into contact with this thing? For example, if you are tested positive for mango, but you usually eat a whole mango without any problems, then you should ignore the result and just eat what you should. If you do get rashes, stomachaches, or even out of breath every time you eat, then take the list to an allergy doctor and make a comprehensive judgment based on your medical history. If you are really unsure, do an oral food challenge test. This is the gold standard for diagnosing food allergy, and it is more accurate than blood draws and pricks.

To be honest, I have seen too many people who were so frightened by a test sheet that they dared not eat or touch anything, and eventually made themselves malnourished: a little girl cut off all eggs, milk and meat in order to "anti-allergy", and was finally diagnosed with iron deficiency anemia, and her hair fell out in handfuls.； An elderly person stopped eating all soy products and seafood that tested positive for the disease, and ended up in the hospital for hypoalbuminemia. It was really because the allergy did not attack, but the disease that frightened him first destroyed his body, and the gain was completely outweighed by the loss.

In fact, to put it bluntly, allergen testing is only a reference tool for doctors, not a judgment to "fast" for you. Your body's true reaction is always much more reliable than the cold test numbers. Don’t scare yourself when you see a list with a plus sign. If you are really unsure, it’s much more useful to see a professional doctor than to make blind choices on your own.