Fruit allergy classification: the truth that it’s fine if you eat it cooked

If you are allergic to fruits, the saying "you'll be fine if you cook them" is only true. Level 3 and below, people with mild to moderate allergies whose allergen is heat-labile protein/pollen cross-allergy Effective. If you have a severe allergy of level 4 or above, or the allergen is a heat-stable protein/small molecule component, you may end up in the emergency room if you eat it dry, let alone cooked.

I met a 16-year-old girl at the allergology department a while ago. Within ten minutes of eating a raw peach, her mouth swelled into a sausage, and her whole body broke out in red rashes. However, she ate canned yellow peaches made at home and grilled peach desserts ordered from takeaways without any problems. I took the allergen report and asked if it was her allergy that had cured itself. Actually no, it just falls within the scope of "cooked food is useful".

Speaking of which, there is no official "fruit allergy classification" in clinical practice. By default, everyone uses the severity classification of food allergic reactions: Level 1 means only redness and itching around the mouth, which can be resolved by itself in half an hour without taking medicine.； Level 2 will spread to the whole body, causing hives and swollen eyelids and lips, which can be suppressed by taking an antihistamine. ； Level 3 may cause mild throat tightness, coughing, nausea and vomiting, but not to the point of difficulty breathing. ； When level 4 is reached, out of breath, low blood pressure, and confusion will appear, which are signs of anaphylactic shock, and you must call 120 immediately. Only people with the first three levels are qualified to discuss the issue of "can it be cooked and eaten?" Patients with level 4 and above, let alone eating, may cause trouble even if they get a little juice from the peel, so there is no need to consider trying it.

Why are some fruits not allergic when cooked? To put it bluntly, these thermally unstable allergens are like a deformed key. They originally fit into the "alert keyhole" of the immune system and trigger an allergic reaction. After being cooked, the structure is completely disintegrated and the immune system cannot recognize it, so it will naturally not sound the alarm. Our common Rosaceae fruits: peaches, apples, pears, cherries, apricots, as well as fresh fruits such as kiwi and strawberry, the main allergens are the PR-10 protein family, which can be completely denatured and inactivated by heating at 60°C for 10 minutes. Especially for people with pollen allergies, such as those who are allergic to birch pollen in spring and wormwood pollen in autumn. Most of the allergies caused by eating such fresh fruits are "cross-allergies" - the PR-10 protein of these fruits looks too similar to the allergen structure of pollen, so the immune system cannot distinguish it and mistakenly attacks it. After heating, the protein structure changes, and naturally they are fine. I have encountered a more interesting case before. A girl was allergic to raw apples, but she could eat a certain freeze-dried apple slice in the supermarket. After checking, I found out that that freeze-drying process went through an instantaneous high-temperature process, which just destroyed the allergens. Another low-temperature freeze-drying one would not work. Do you think it is mysterious?

But not everyone has this blessing. I also met a young man at the outpatient clinic who said he was allergic to raw mangoes. He read on the Internet that boiled mango syrup was edible. After cooking it for 20 minutes, he still had rashes all over his body and could not breathe after taking two mouthfuls, so he was sent to the emergency room. This is the pitfall of "heat-stable allergens": the main allergen Pan m 1 of mango, the lipid transfer protein Pru p 3 of peach, and the phenolic components of pineapple. These substances are either extremely heat stable and are still active after being cooked at 100°C for half an hour, or they are not proteins themselves and heating will not change the structure at all. No matter how you process them, the immune system will still recognize them and trigger allergies. Especially for people who are allergic to lipid transfer proteins, allergic reactions are generally severe. Even eating processed preserved fruits and jams may cause them, so don't touch them blindly.

There are currently two schools of thought in the industry on whether people with mild to moderate allergies should try eating cooked fruits: Doctors who are more radical will think that this is a good oral immune tolerance aid. They should start with a small dose of ripe fruits and slowly transition to a small amount of raw fruits. Maybe they will gradually become desensitized.； Conservative doctors believe that there is no need to take this risk. After all, even if the risk is only one in 10,000, it is 100% if it falls on an individual. It is safer to avoid it directly. My own experience after follow-up consultation is that whether you should try it or not depends entirely on your personal needs: if you are a food addict, you should first do a precise allergen component test to make sure that your allergens are heat-labile and the allergy level is below level 3. Then you can take a small sip of cooked fruit pulp to test your sensitivity. If there is no reaction, then slowly increase the amount. ； If you don’t like food that much, there is no need to take this risk.

Oh, by the way, don’t think that as long as it is cooked, it is absolutely safe. The fruit pies and canned fruits sold outside may not be fully cooked. Some processing is just a superficial heating, and the residual allergens are enough to induce reactions. Some people think, "I just feel a little itchy when eating raw food, so it's not an allergy." In fact, that's a sign of a level 1 allergy. Repeated stimulation may one day escalate to level 3 or 4, so don't take it seriously.

In the final analysis, there is never a unified standard answer to the matter of eating fruit. Just because someone else is fine with it does not mean that you are fine. Knowing your own body's bottom line is more reliable than any folk remedies.