Food allergy and intolerance

　　There are many reasons for food intolerance, including enzyme deficiency, special chemical components in food, and the destruction of the gastrointestinal barrier function, which makes the human body unable to fully digest food macromolecules, leading to a series of symptoms.

　　1. Anaphylactic shock:Anaphylactic shock is an acute systemic reaction that occurs in the human body due to an allergic reaction to certain biological products (such as heterologous serum) or drugs (such as penicillin, iodinated contrast agents). The manifestations and severity of anaphylactic shock vary greatly depending on the body's reactivity, the amount and route of antigen entry. It usually occurs suddenly and is very severe, and if not treated in time, it can often be life-threatening.

　　2. Fatal asthma:Asthma is a chronic airway inflammation involving various cells, especially mast cells, eosinophils, and T lymphocytes. In susceptible individuals, this inflammation can cause recurrent episodes of wheezing, shortness of breath, chest tightness, and (or) cough, which often occur at night and (or) in the early morning, and the airways react hyperactively to various stimuli.

　　3. Gastrointestinal edema:Excess fluid accumulating in the tissue spaces or body cavities is called edema (edema). Only a small amount of fluid is normally present in the body cavities, and if fluid accumulates in the body cavities, it is called effusion.

　　Adult patients are usually clear about severe food allergies. If it is unclear or in most children, diagnosis may be difficult, and it needs to be distinguished from gastrointestinal functional disorders.

　　For suspicious patients who have a food reaction after eating, a corresponding skin test can be used first to determine the relationship between the symptoms and the food. A positive skin test does not confirm that the clinical symptoms are related to allergy. However, a negative test can exclude the relationship with allergy. When the skin test is positive, the elimination diet method can be used to determine the relationship between the symptoms and food allergy. If the symptoms improve, the food can be given again to determine whether it can induce symptoms. All positive challenge tests should be followed by double-blind challenge tests to confirm the diagnosis. The elimination diet method is to exclude the suspected food that can cause symptoms from the basic diet, or to use a diet composed of relatively non-allergenic foods.

　　Common foods that cause allergies include milk, eggs, shellfish, nuts, wheat, peanuts, soybeans, and all foods containing one or more of the above ingredients. Most common allergens and all suspicious foods should be excluded from the diet from the beginning. Other foods or liquids cannot be eaten or drunk other than those specific diets at the beginning. It is not advisable to go to restaurants to eat, as the patient (and the doctor) need to know the exact composition of each dish. In addition, it is necessary to frequently understand the purity of the food used. For example, a common rye bread contains some wheat flour.

　　If the given diet does not improve after one week, the diet should be changed. If the symptoms are relieved, a new food can be added to the diet and eaten in excess of the usual amount for more than 24 hours or until the symptoms recur. Another method is to eat a small amount of test food in the presence of a doctor and observe the patient's reaction. The appearance of symptoms worsening or recurrence after adding new food is the best evidence of intolerance to that food. This evidence needs to be verified, that is, the food is removed from the diet for several days and then added back to observe the effect.

　　Once food that needs to be avoided is found, not only should it be excluded from the diet, but also the habit of checking the ingredient list before buying food should be formed, so as to better protect oneself. In addition, being intolerant to a certain food does not mean that it can no longer be eaten. To eat a certain food again, a gap of at least 1 week should be kept. During the 'trial eating' period, a simple product of this food should be chosen, for example, if dairy products are to be avoided, active yogurt can be eaten first, and if no symptoms appear for more than 5 days, milk can be tried, otherwise other dairy products should not be tried.

　　In addition to relying on clinical manifestations, related auxiliary examinations are also indispensable for the diagnosis of food allergies and intolerance.

     1. Blood test for food tolerance test.

　　2. Allergen testing.

　　Common allergens that usually cause allergies include milk, eggs, shellfish, nuts, wheat, peanuts, soybeans, and all foods containing one or more of the above ingredients. The diet should exclude most common allergens and all suspected foods from the beginning. No other food or liquid should be consumed in the initial diet except for specific diets. It is not advisable to go to restaurants to eat, as both the patient (and the doctor) need to know the exact composition of each dish. In addition, it is necessary to frequently understand the purity of the food used. For example, ordinary rye bread contains some wheat flour. If the given diet does not improve after a week, it should be changed. If the symptoms improve, a new food can be added to the diet in an amount greater than usual and eaten for more than 24 hours or until the symptoms recur again.

　　There is no special treatment other than excluding the offending food. An exclusion diet can be used for both diagnosis and treatment. If it is only related to individual foods, it is advisable to fast. Sensitivity to one or more foods can spontaneously disappear. Oral desensitization (firstly excluding the offending food for a period of time, then starting with a small amount and gradually increasing daily) and sublingual administration of food extract for desensitization have not been proven effective. Antihistamines are rarely valuable unless there are acute systemic reactions such as urticaria, angioedema, etc. Sodium cromoglycate is effective in other countries, but in the United States, it is only approved for use in oral agents for mastocytosis. Long-term use of corticosteroids for other than eosinophilic enteropathy has no indication.