food allergy blood test

cannot. The food-specific IgE blood test currently commonly used in clinical practice can only be used as an auxiliary screening tool for immediate food allergy. The positive predictive value fluctuates between 50% and 90%. The specific reference value must be judged based on the actual eating reaction. You must not rely on a blood test report alone to avoid certain types of food for a long time.

Not long ago, my sister's baby just entered kindergarten and kept rubbing her eyes and sneezing. Her mother was so worried that she spent more than 2,000 yuan to find an agency online to test more than 100 food intolerances. She said she was allergic to mango, cod, and tomatoes. As a result, the kindergarten ate mango pancake last week, and the baby rushed to eat two. Nothing happened. Do you think the money was spent unjustly?

In fact, this situation is so common that many people can’t figure out the difference between the two types of “allergy blood tests” on the market, and there are many mistakes. The blood test we often talk about that is really related to food allergies checks for food-specific IgE, which is aimed at immediate allergic reactions - the kind that causes mouth swelling, hives, and even breathlessness within half an hour of eating something. The higher the value of this type of test, the greater the probability of true allergy. For example, if peanut IgE is greater than 15kUA/L, more than 90% are indeed allergic to peanuts, which is of high reference value. But if it is IgG, which is what businesses often call "food intolerance testing", then the controversy will be great.

At present, the mainstream allergology community, including the World Allergy Organization (WAO), clearly does not recommend food IgG testing as a diagnostic basis for food allergy - many healthy people will also test positive for IgG. This is essentially a normal immune memory generated by the body after contact with food, and is not an allergy signal. If you follow this report, you are just looking for trouble. I have seen the most outrageous reports when I was accompanying patients in the allergy department. Some people tested positive to rice and pork. If they were all avoided, they would basically have to drink northwest wind, which is completely unrealistic.

Of course, this does not mean that IgG testing is completely useless. There are indeed some clinical cases in functional medicine and gastroenterology that show that for some patients with chronic diarrhea, intractable eczema, and recurrent migraines who have no cause for a long time, if the IgG test is positive for a high titer of a certain type of food, the symptoms will indeed be significantly relieved after 2-4 weeks of targeted taboos. This part of the clinical research is still in progress. There is currently no unified consensus, so there is no need to overturn it all at once.

Speaking of serious allergy blood tests, you have to be careful to avoid pitfalls: don't believe in "allergy tests" such as nail tests and hair tests. A serious allergy blood test is to draw venous blood, and the error of fingertip blood is very large, let alone those fancy sampling methods. And even if the IgE test is positive, it does not necessarily mean that you cannot eat it. For example, if you test positive for milk, but you don’t have any reaction to drinking milk tea or eating cheese, then there is no need to avoid it at all. Oral food challenge test is the gold standard for food allergy diagnosis. Blood test is at best a "stepping stone" to help you narrow down the scope of investigation.

In a word, allergy blood tests are not a scourge, nor are they a panacea. Don’t rush to make a list of taboos after you get the report. Ask an allergist at a regular hospital to evaluate the actual situation. It is much more reliable than guessing on Baidu and starving your baby.