Adverse reaction to food (adverse reaction to food) refers to all adverse reactions caused by food ingredients or food additives, divided into toxic reactions and non-toxic reactions, anyone who eats sufficient amount of contaminated food will react. According to the pathogenesis, it is divided into food intolerance and food allergy. Food intolerance does not involve the immune mechanism, and the most common one is lactose intolerance. Food allergy is defined as an immune-mediated adverse reaction of the body to antigenic substances in food. The clinical manifestations of food allergy are diverse, the most common being gastrointestinal symptoms, skin mucosal symptoms and respiratory symptoms. The main food allergens that pose a threat to human health come from foods containing allergenic proteins, food additives used in food processing and storage, and genetically modified foods that contain allergens. More than 90% of clinical allergic reactions are caused by eight types of highly allergenic foods: eggs, fish, shellfish, milk, peanuts, soy, nuts and wheat. Other foods such as pork, beef, chicken, corn, tomatoes, carrots, celery, mushrooms, garlic, sweet peppers, oranges, pineapples, kiwi, mustard, and yeast induce fewer allergic reactions. Food allergy is more prevalent in infants and children than in adults. Food allergy predominates in infants and young children (under 3 years of age), and sensitivity to inhaled antigens increases in children over 4 years of age. The incidence decreases with age. 56% of children are no longer allergic to milk at age 1, 70% at age 2, and 87% at age 3. The highest prevalence of food allergy is seen in young infants between 0 and 6 months of age, with gastrointestinal symptoms as the main clinical manifestation, including persistent colic; vomiting, diarrhea and blood in the stool, and loss of intestinal proteins. These symptoms can occur suddenly and can be mild or severe or even life-threatening, and in infants and toddlers older than 6 months of age, skin lesions such as eczema, polypoid rash, and rubella are the main manifestations. Chronic food allergies can lead to poor growth and development in infants. Anaphylaxis is the most serious food allergy reaction and can be life-threatening. The prevalence of allergy is low, but symptoms are often severe and persistent, and food antigens play an important role in allergic diseases such as allergic asthma and glomerulonephritis. Since the foods that cause allergies in children are mainly protein-rich and necessary for growth and development, failure to accurately diagnose food allergies, select appropriate food substitutes for children and provide nutritional guidance can lead to secondary malnutrition, and missed or misdiagnosed diagnoses can affect the growth and development of children and even cause serious consequences. The main risk factors for food allergy are a positive family history of allergic diseases, exclusive breastfeeding for less than 4 months, and improper addition of complementary foods. Genetic factors play a major role in allergic diseases. If one parent has allergic diseases, the prevalence of food allergy in their children is 30%-40%; if both parents have allergic diseases, the prevalence of their children is as high as 60%-80%. Breastfeeding for too short a time and improper addition of complementary foods are closely related to food allergies. The risk of food allergy is 1.35 times higher in infants who are introduced to complementary foods within 4 months of age than in those who are introduced later, and food is probably the most important environmental allergen to which infants are exposed. For children at risk with a family history of allergic disease and elevated serum IgE levels, their mothers should avoid allergy-prone foods during pregnancy and lactation, and delaying weaning and the addition of dairy products, eggs, fish, nuts, and legumes may be able to reduce the child’s allergy rate and alleviate symptoms. For children at high risk of food allergy who have to be mixed or hand-fed for various reasons, feeding hydrolyzed formula may be effective in reducing the incidence or alleviating the symptoms of food allergy.