Pollen-food cross-reaction: Be careful with these fruit and vegetable allergies

If you are a pollen allergy sufferer and often experience numb lips, itchy throat, and skin rashes when eating fresh fruits and vegetables, it is most likely not that the fruits and vegetables are not washed well, nor that you are allergic to the fruits and vegetables themselves, but that a "pollen-food cross-reaction" is triggered - the immune system will mistake proteins in fruits and vegetables that are highly similar to pollen structures for invading pollen, thereby triggering an allergic reaction. In severe cases, it may even cause laryngeal edema and anaphylactic shock.

Let’s talk about an example I encountered in the clinic last week: a 22-year-old girl was highly positive for mugwort pollen. She suffered from rhinitis in August and September every year to the point where she couldn’t even sleep well. In the past two years, she always felt itchy in her throat when eating fresh dates in the autumn.

This principle is very easy to understand. Just like face unlocking on a mobile phone, it is easy to identify twins. As long as the three-dimensional structures of the two proteins have similar fragments, the immune system that has been "trained" by pollen to be highly sensitive will start the defense mechanism regardless of the situation. Oh, by the way, most of the proteins that can trigger cross-reactivity are thermally unstable. To put it bluntly, they are denatured and inactivated when heated. Many people say that they are allergic to eating raw peaches, but eating canned yellow peaches and grilled preserved peaches is not a problem at all. This is the essence of the reason.

At present, there is a large statistical difference in the incidence of cross-reaction among people with pollen allergies in the academic community. Some rumors say that about 30% of pollen allergy patients will have such reactions, and some clinical data believe that it can reach 50%. After all, many people only have a slight numbness in the mouth and get better in two minutes. They do not think about allergies at all and do not go to the hospital. The correspondence we encounter most often is actually not that complicated: People with Artemisia pollen allergies are likely to have problems when exposed to fresh dates, kiwis, cantaloupes, and coriander. ； Those allergic to ragweed pollen should be careful with bananas, cucumbers, and melons ； Patients who are allergic to birch pollen are particularly likely to be affected by eating raw apples, cherries, hazelnuts, and carrots.

There is no unified standard answer in clinical practice as to whether to completely avoid corresponding foods due to cross-reaction. One school of thought is that as long as you have symptoms, you should avoid food completely. After all, the risk of triggering a severe allergic reaction is too high. ； However, many allergist doctors I have met are more inclined to "make decisions based on symptoms": if you only have mild numbness in the lips or itchy throat, you can try to heat the food before eating it, and you don't have to cut it out completely - after all, the nutrients of many fruits and vegetables are difficult to replace. If you don't eat them completely because of minor symptoms, it will greatly affect your quality of life. I used to follow up with an uncle who was allergic to birch pollen. His lips would swell within a minute of eating raw apples. Now he steams the apples into sweet soup or bakes them into apple pie. There is no problem after eating them. There is no need to stock up on desensitizing drugs during the pollen season every year.

Don't tell me, many people don't understand the difference between cross-reactivity and true food allergies. There was a young man who always thought he was allergic to mangoes and did not even dare to touch mango-flavored drinks. Later, after some research, he found out that he was allergic to humulus pollen. The protein in raw mangoes has a similar structure to humulus pollen, which triggers the reaction. It is perfectly fine to eat heated dried mangoes and mango jam. Now he eats dried mangoes as snacks every day.

Of course, there are situations where you need to be particularly careful: if after eating a certain food, you not only experience slight local discomfort, but also develop wheals, breathlessness, abdominal pain, and dizziness all over your body, don’t hesitate. It is most likely not an ordinary cross-reaction, but you may be allergic to the tolerant protein of this food. In this case, you must not only avoid the food completely, but also carry an emergency epinephrine pen with you.

Oh, by the way, there are many people who don’t even know that they are allergic to pollen. They only know that they feel uncomfortable eating certain fresh foods. In fact, if you go to the hospital to check the pollen-specific IgE, you can basically identify the cause, saving you a long time of guessing and not knowing how to avoid it. To put it bluntly, there is never a one-size-fits-all standard answer to allergies. Your own body's reaction is the most accurate reference. There is no need to bear it or be overly anxious. Once you understand the rules, you should eat and drink as you should, and there are not so many things to avoid.