Link between food allergies and respiratory diseases

At present, the global allergy community has reached a consensus that food allergy and respiratory diseases such as allergic rhinitis, asthma, and eosinophilic bronchitis are highly related "immune comorbidities". The two share the core pathogenesis of Th2 pathway abnormalities. About 38% to 45% of food allergy patients will develop respiratory symptoms simultaneously. For people with allergic respiratory diseases, the risk of food allergy is 2.3 to 3.1 times higher than that of healthy people.

I just encountered a typical case at the allergy clinic last week: every time 6-year-old Haohao eats mango, he will first develop a small red rash around his mouth. In about half an hour, he will start rubbing his nose and sneezing seven or eight times in a row. In severe cases, he will hear the sound of a bellows in his throat. In the past, parents always thought that their child just caught a cold. It was not until he came to the doctor this time with severe wheezing. The allergen test showed that the concentration of mango-specific IgE was as high as 12.6kUA/L, and the lung function also showed mild airway hyperresponsiveness. Only then did they connect the food allergy and repeated wheezing.

To put it bluntly, it is easy to understand. Our immune system is like the security team of a community. Its original duty is to catch external bad guys such as viruses and bacteria. As a result, the security team misunderstood some people with sensitive constitutions and regarded milk, eggs, peanuts, mangoes and other originally harmless foods as intruders. When they first came into contact, they issued a "wanted order" with a photo - that is, specific IgE antibodies. These antibodies are not just guarding the gastrointestinal tract. They can travel along the blood circulation and attach to the nasal mucosa, airway mucosa and even mast cells under the skin, which is equivalent to being posted in the entire community. The next time you eat this kind of food, the whole body will sound the alarm at the same time, releasing inflammatory substances such as histamine and leukotrienes. Not only will the gastrointestinal tract be upset, the skin will be rashed, the nasal mucosa will be blocked and sneezed due to edema, and the airway will be contracted, causing coughing and wheezing. Respiratory symptoms will naturally appear.

Interestingly, the academic community has not yet reached a completely unified conclusion regarding the causal relationship between the two. One group of scholars insists that this is an extension of "the same disease in the same airway" and believes that allergy is a systemic immune disorder. Food allergy is often the first step in the allergy process: eczema and food allergy first appear in infancy, and then slowly develop into allergic rhinitis as they grow older, and finally progress to asthma, which is a linear development process. But the clinical evidence for the other group is also strong: they followed 1,200 children with food allergies to the age of 12 and found that more than 60% of the children developed tolerance to the food they were previously allergic to by the age of 6, and did not develop any respiratory diseases. ； On the contrary, nearly 20% of children with no history of food allergies later develop food allergies due to long-term exposure to high concentrations of dust mites and pollen. For example, what we often call "pollen-food allergy syndrome" is the best example: People who are allergic to birch pollen may suddenly experience numbness in the mouth, itchy throat, or even induce rhinitis attacks if they eat apples, cherries, carrots and other foods that have cross-antigens with birch pollen, even if they have been fine for decades.

Believe it or not, I have a 32-year-old female patient who had been fine after eating apples for more than 20 years. Last spring she started suffering from birch hay fever. This year, she started sneezing and had a runny nose within ten minutes of taking the first bite of a fresh apple. She thought she had a cold. After she came for a check-up, she found out that it was caused by cross-allergy. There was a junior high school student whose asthma had been under unstable control for more than half a year. Every time he had an attack, he would go back to his grandma's house on weekends. After asking around carefully, he discovered that grandma would make him pork rib soup with peanuts every time. After he banned peanuts, he cut the amount of inhaled hormones in half, and he didn't have an asthma attack in almost three months.

When it comes to treatment, current clinical opinions are not unanimous. Doctors of the older generation often say that since it is found that you are allergic to a certain food, you should strictly avoid it and don't touch it, and you will be fine. However, the new guidelines issued by the World Allergy Organization (WAO) in the past two years have actually adjusted their recommendations: If IgE is only detected but there have never been any allergic symptoms, whether it is skin, gastrointestinal or respiratory tract, blind taboos are not recommended, especially for children. Blind taboos will lead to insufficient nutritional intake, which will disrupt immune balance and increase the risk of respiratory diseases. There is also a more cutting-edge research that believes that on the premise of controlling airway symptoms, gradually introducing low-dose allergenic foods to induce tolerance can reduce the frequency of respiratory disease attacks at the same time. Last year, we had a young patient with asthma and peanut allergy who underwent oral tolerance induction for half a year. Not only can he eat peanuts in small amounts, but the number of asthma attacks has also dropped from an average of 2 times a month to once every half a year. The effect is really surprising.

In fact, until now, there are still many mechanisms between food allergies and respiratory diseases that have not been fully understood, and there are few clinical solutions that are universally applicable. After all, everyone’s immune system is unique. What I usually tell my patients the most is, don’t make blind guesses at the symptoms on the Internet, and don’t blindly avoid food with the allergen test report. If you really suspect there is a correlation, keep a diet and symptom diary, and find a professional allergist for evaluation. This is better than anything else.