The difference between food intolerance and allergy

Food allergy is an acute/chronic allergic reaction mediated by IgE and other immune systems. It is not dose-dependent and can be fatal in severe cases.； Food intolerance is mostly a non-immune-mediated metabolic abnormality or local irritation reaction. Most of them have a dose threshold and are rarely life-threatening. This is the most essential difference between the two.

Two weeks ago, I met a junior high school student during a follow-up visit in the nutrition department. Her mother dragged her here and said that the child gets rashes every time he eats shrimp. I had heard people say that it might be a "small problem" intolerance, and they deliberately gave him two less mouthfuls at a time to "break the tolerance." As a result, he was out of breath after eating two last time and was sent to the emergency room. After checking the allergens, he found out that it was a serious shrimp allergy. If he feeds him randomly, something serious will happen. To be honest, many people can't tell the difference between the two. Essentially, they don't understand that the logic of physical problems is completely different - for example, allergies are equivalent to your immune system convulsing and treating harmless food ingredients as invading terrorists. Even if they sneak in even a little bit, IgE antibodies will be dispatched to initiate a "city-wide martial law". The movement will be loud, ranging from swollen and itchy skin to edema and shock in the throat. ； Intolerance is more like a lack of capacity in the digestive assembly line of your intestines and stomach, such as a lack of lactase or enzymes that decompose gluten. If you stuff too much at once and exceed the capacity, the remaining residue will ferment in the intestines and cause trouble. At most, the workshop will be a mess with diarrhea and bloating, but it will definitely not blow up the factory.

There is another reason why many people get confused: the symptoms of the two are sometimes very similar, including rashes, diarrhea, headaches, and lack of energy, and you can’t even tell what the problem is. In fact, you can do a preliminary screening at home. The most intuitive way is to see if there is any "accident caused by touching it". I have seen a girl who is allergic to peach hair. If someone rubs a peach against her face, half of her face will swell. This is definitely an allergy. ； If you take a sip of yogurt and nothing happens, but after three cups in a row you squat on the toilet and can't get up, then you are basically lactose intolerant and have nothing to do with allergies. Looking at the speed of onset, most allergies come on quickly, with reactions occurring within a few minutes to two hours. Delayed allergies rarely exceed 24 hours. ； Intolerance is much slower. Many people eat half a plate of cheesecake the night before, only to have headaches and acne the next afternoon, without thinking that it is a food problem.

Speaking of this, someone must ask, can I do the food IgG test that is very popular on the Internet? I have to say something heartfelt here. There is quite a quarrel in the industry about this test, and there is no unified conclusion. Some clinical nutritionists believe that elevated serum IgG can be used as a reference for dietary adjustments. I have encountered patients with repeated urticaria before. If they stopped the corresponding high intolerance foods according to the IgG report, the rash disappeared within two weeks. ； However, the mainstream view of the allergist department is that there is currently no uniform positive criterion for IgG testing, and it cannot be directly equated with intolerance. Many people have been found to have high IgG levels against eggs and milk, but have no problems with whatever they eat. They have suffered from not eating for three or four months, but they have not been able to get enough protein. If you really want to check whether you have an intolerance, you might as well spend a few dollars to buy a food diary and keep a food diary for two or three weeks. What you ate, how much you ate, and any reactions in the next day or two. Compare the results before and after.

There is also a widely circulated misunderstanding that "allergies occur in childhood and disappear as adults, while intolerance lasts a lifetime." This is not entirely true. It is true that many children's allergies to milk and eggs resolve on their own by the time they reach school age, but some people are allergic to nuts and seafood for a lifetime. ； If you are intolerant, you may be able to adjust. For example, people who are lactose intolerant drink warm milk in small amounts and multiple times a day, which slowly induces an increase in lactase activity. Many people end up drinking 200ml of whole milk without any problems. I once had a patient who used to have diarrhea after just one sip, but now drinks it with bread every morning and it tastes great.

Of course, don’t be too anxious. If you feel uncomfortable after eating something, don’t label it as an allergy or intolerance. Maybe it’s because you had too much iced milk tea and spicy hot pot that day. If the same reaction occurs repeatedly and you can't figure it out, go directly to the allergology department or nutrition department of a regular hospital to ask. Don't make blind choices and deprive yourself of nutrients.