With the acceleration of industrialization and the great satisfaction of material life, there is an increasing trend of allergic diseases in children, which causes a lot of trouble for parents. Parents of allergic children are always eager to ask: what can I do to avoid my baby’s allergy? Allergic diseases are relatively complicated and there are many ways to avoid them, including drug prevention, avoiding contact with allergens, avoiding air pollution and dietary taboos. However, the prevention of food allergy is relatively simple, that is, avoid eating allergic foods. As the child’s digestive function is perfected and the intestinal tract matures, food allergy will be significantly reduced. The following is a discussion of the occurrence of food allergies and the various symptoms: allergies are complicated because allergic diseases involve a wide range of cytokines and antibodies. Among the antibodies, there are not only IgE antibodies, which are familiar to all of us, but also IgG antibodies for delayed-onset allergic reactions, which can directly activate eosinophils, basophils and mast cells by combining with antigens, releasing inflammatory mediators and causing edema and acute inflammation of skin and mucous membranes, and this is the rapid-onset allergic reaction, and the symptoms usually appear within half an hour or two hours of encountering the allergens. For example: itchy eyes caused by pollen in spring and fall: allergic conjunctivitis; sneezing and runny nose: allergic rhinitis; coughing and wheezing caused by dust, mites or animal fur; asthma. These problems are very regular and repetitive, and are easily detected and prevented by patients and doctors. IgG antibodies, on the other hand, are much more complex. Since they are a factor in the body’s resistance to various infectious diseases, the body contains many of them, and it is easy to overlook them and consider specific IgGs of little significance. We look at the evolution of antibodies to see how antibodies are formed, antibodies is the process of human development in order to fight against foreign invasion of the formation of natural immunity products, when the invasion of foreign objects, antibodies and foreign substances (which we call antigens) combined, so that the foreign object is more significant and easy to identify, and then mobilize the body’s resistance to various factors to kill the foreign object, these resistance factors include phagocytes and natural killer cells (the body’s natural killer cells), and then mobilize the body’s various resistance factors, including phagocytosis. Natural killer cells (the body’s police force, small in number and highly mobile). IgE antibodies, which we call antibodies with little effect, were produced mainly to fight parasites. Thousands of years ago, human ancestors lived mainly in the wild, mainly on raw food, with a lifespan of only about 30 years, and the main diseases were parasitic infections, and the main weapon of defense for human beings was IgE antibodies. As living as well as housing conditions improved, parasitic diseases became less and less common. And human instinctive combat ability has not degraded, and with the increase in living standards also strengthened, IgE antibodies first of all to some harmless inhalation of things as a foreign object to resist, a strong exclusion reaction occurs, is what we say allergic reaction. Especially the pollutant PM10, the bigger the pollutant, the stronger the resistance, that is, the stronger the allergy. PM2.5 is relatively small, can freely enter and exit the respiratory tract along with the breathing and even reach the fine bronchial tubes directly, directly causing damage to the respiratory mucous membranes, due to the small size of the IgE antibody does not think it is a harmful invasion, so it is not a great relationship with the allergy. Because IgE antibody is relatively large, mainly free in the mucous membrane layer, so it fights against mainly inhalation allergens, and part of the food allergens through the intestinal mucosa, so the manifestation of the symptoms of the mucous membrane is mainly mucous membrane, such as: itchy eyes, itchy nose, sneezing, coughing, gastrointestinal mucous membrane manifestation is stomach pain and diarrhea. So when we say that IgE is a pitfall of human evolution, it’s nothing! IgG antibodies are the main human factor in the fight against all kinds of diseases, in large quantities and powerful, equivalent to the army of the human body, and together with the white blood cells, form the national defense system. The vaccines we get are designed to produce specific IgG to fight various serious infectious diseases. In fact, IgG is also a militant, always monitoring all kinds of changes in the body, to guard against the invasion of the enemy. If this guard is overpowered, a good thing can become a bad thing. This is the case with food allergies. Various proteins have to be broken down into amino acids or short peptides composed of several amino acids through the body’s digestive system and absorbed into the body before they can be absorbed and utilized. However, due to the imperfect development of the child’s digestive system and immature development of enzymes, resulting in the protein can not be completely digested and broken down into amino acids or short peptides, a significant portion of the polypeptides (more than 10 amino acids), the child’s intestinal barrier is also immature, these polypeptides will be absorbed into the blood. The human body instinctively recognizes amino acids and short peptides, but not peptides, and considers peptides to be foreign invaders, and thus the body produces IgG antibodies for labeling and conjugation to kill and exclude this type of peptide material, which is how food allergy occurs. This exclusion and defense is not gentle, but a fierce battle that results in a flurry of activity. IgG antibodies have a relatively small molecular weight, and after binding to the antigen they cannot be eliminated in situ by phagocytes, the police force, and can reach all parts of the body with the bloodstream, where a more complex immune response takes place with the participation of complement, which occurs not in a rapid but in a delayed fashion. So unlike the IgE-mediated mucosa-based manifestations, IgG-mediated allergic reactions are systemic reactions, and delayed-onset allergic reactions can have the following symptoms: 1, digestive tract: abdominal pain, diarrhea, constipation, mouth ulcers, flatulence, etc.; 2, skin: eczema, urticaria, dryness, hyperkeratosis, acne, etc.; 3, nerves: dizziness, migraines, sleep disorders, febrile convulsions, epilepsy, etc.; 4, mental: Anxiety, depression, hyperactivity, inattention, irritability, etc.; 5, respiratory: asthma, chronic cough, chronic rhinitis, sinusitis, snoring, etc.; 6, musculoskeletal: arthritis, joint pain, etc.; 7, genitourinary: urinary frequency, urinary urgency, vaginal itching, etc.; 8, cardiovascular: chest pain, hypertension, cardiac arrhythmia, etc. Food allergy is the most important is a protein allergy, especially some of the molecular weight of the protein, such as egg protein and milk protein, such as egg protein and milk protein. Proteins, such as egg protein and milk casein, these protein molecules are relatively large, it is difficult to completely digest and decompose into amino acids and short peptides, it is easy to be allergic to, when absorbed into the blood peptide is excluded from the body, the human body will have a relative protein deficiency, so that there are some other symptoms. For example, dry hair, no luster, dry skin, dark skin, slow growth and development, there is a decline in resistance. The body’s resistance includes white blood cells, antibodies and a variety of biological factors, the human body itself is a state with bacteria, the vast majority of bacteria are harmless bacteria, no harm to the human body. There are also a small number of harmful bacteria, but can not make waves, because the human body has these guards, and is in a state of balance. When the number of harmful bacteria invasion increases, the body will automatically mobilize more resistance to participate in the fight. This state requires the body to have a reserve of weapons, or a reserve of raw materials, which can be supplied when the organism needs them. The main component of white blood cells, antibodies and biofactors are proteins, which basically have to be replaced once every 3-7 days, and the body already needs to have quality proteins to safeguard them. When allergic children consume eggs and milk (considered high-quality protein), part of the protein in the body will be combined with antibodies, the body can not be utilized, excreted through the kidneys, resulting in a relative lack of protein, this relative lack of usually can not be seen, but when encountered with a more virulent viruses or bacteria, it is difficult to cook, the body can not make more weapons, resulting in resistance Relatively insufficient, it will form a decline in immunity. The best way to prevent food allergy is to avoid allergic foods and to check for food allergens in time, including quick-onset and late-onset allergies. The following children in particular are the focus of the checkups: 1. Those who have had pneumonia or bronchitis twice before the age of 6 months, those who suffer from severe eczema or recurrent eczema, and those who have had bronchitis or pneumonia for three times before the age of one year. 2. Those who have developed jawbone problems around the age of one year, or those who have developed jawbone problems around the age of one year. 3. 2. Jaw shaking or involuntary shaking of the whole body or part of the body around the age of one year. 3.Repeated burping, farting, crying, diarrhea or constipation. 4.Sleeping with mouth open or snoring before 2 years old. 5.High fever convulsions before 3 years old.