The development of allergic diseases has its natural process (atopic march), that is, at a specific age, the successive appearance of characteristic clinical manifestations of allergic reactions, and continue for many years, with age, certain symptoms may dominate, while others reduce or disappear completely, usually children atopic dermatitis (eczema) and food allergies are the first symptoms, gradually develop into allergic rhinitis, and eventually leading to asthma. Atopic dermatitis (eczema), allergic rhinitis and asthma are common conditions, especially in Western countries, and their incidence has been increasing in recent decades. Eczema is a chronic recurrent infectious skin disease with itching, mossiness and scarring, and is the most common infectious skin disease of childhood, usually starting within the first year of life. The prevalence of eczema is 10-20% in children and 1-3% in adults, 17.2% in children aged 5-9 years, and 0.3-20.5% in children aged 13-14 years, especially in developed industrialized countries, the prevalence of eczema in the upper class and people living in urban areas is increasing. 35-40% of children with food allergies have both food allergies and atopic dermatitis, and the prevalence of food allergies is higher than the prevalence of eczema in children. Food allergy and atopic dermatitis occur together in 35-40% of children, and the prevalence of food allergy peaks in children at 2 years of age, increases to 6-8% at 1 year of age, and decreases to 1-2% in adulthood. In recent years, a number of studies have confirmed the natural course of allergic diseases, in which atopic dermatitis and food allergy are the first manifestations in childhood, persisting for many years and progressing to allergic rhinitis and asthma. A survey of 2,222 infants aged 11.5-22.5 months with eczema found that 64% of infants with eczema presenting within 3 months of birth were sensitized to IgE-mediated allergies to egg or milk or peanuts, and that the proportion of such sensitivities increased with the severity of eczema in infants up to 12 months of age, a phenomenon which did not manifest itself in children with eczema after the age of one year. . By adulthood, even fewer of those with eczema are allergic to food. There has also been much research into the relationship between eczema and allergic rhinitis and asthma. It has been shown that more than half of children with severe atopic dermatitis eventually develop asthma and about 75% develop allergic rhinitis. The presence of eczema in children before the age of 2 years, especially within the first 6 months of life, is a high risk factor for the development of allergic rhinitis and asthma by the age of 6-7 years, and is more pronounced in boys, where the rate can be as high as 45%. Recently, the impact of eczema on the persistence of childhood asthma into middle age has been suggested for the first time in a retrospective study, with significant correlations between childhood eczema and new-onset asthma at three different life stages: pre-puberty, puberty, and adulthood, as well as persistent asthma from 8-44 years of age. A number of studies have also shown a strong association between childhood allergic rhinitis and subsequent asthma. Between 10-40% of patients with allergic rhinitis also have asthma, and up to 80% of patients with asthma also have allergic rhinitis. All of the above studies confirm the natural course of allergic diseases and shed good light on their interrelationships. It is by focusing on prevention for a genetically determined individual child susceptible to allergic diseases that the natural course of allergic diseases may be fundamentally altered. (i) Food prevention In 2001, WHO advocated exclusive breastfeeding for more than 6 months because the early addition of complementary foods (exogenous protein antigens) is detrimental to the conversion of the immune system Th2 to Th1 in early infants lacking Treg cells, leading to the development of Th2 dominant allergic reactions. In the last two years, a large number of new studies have disproved the previous theory and concluded that exclusive breastfeeding with delayed (>6 months) complementary food intake not only does not reduce the incidence of allergic diseases, but on the contrary increases their incidence while being detrimental to the health of the infant. The rate of peanut allergy among Jews living in Israel was much lower than that among Jews who migrated to the United Kingdom because the former ingested more peanuts in early childhood, suggesting that oral exposure to food allergens may play an important role in inducing tolerance to food allergens. It has been suggested that the reason for the damage to the organism and increased allergen sensitization by delayed complementary food intake is that the optimal period (4-6 months) for critical and effective transoral induction of immune tolerance in infants is missed. It is well documented that a high intake of fruits, vegetables, legumes, seafood and whole grains, and a low intake of trans-fatty acids and monosaccharides during the mother’s pregnancy and childhood can be effective in reducing the risk of developing allergic diseases. (ii) Environmental prevention The environment has an important influence on the development of allergic diseases. In particular, soot produced by smoking is an important cause of asthma and other allergic diseases. It has been shown that smoke in the environment from smoking can increase the risk of allergic sensitization and asthma in children. Therefore, all parents are strongly advised to quit smoking. Dust mites are common allergens in the environment, and it has been suggested for the first time through research studies that strict avoidance of dust mites and highly antigenic foods can reduce allergen sensitization in infants in high-risk groups. As with the hygiene hypothesis, exposure to microorganisms in childhood reduces the chances of developing allergic diseases, but it should also be noted that respiratory viral infections are a high risk factor for developing asthma. (iii) Medical therapy In recent years, there have been dramatic advances in specific immunotherapy, which can be effective in alleviating the symptoms of allergic disease and reducing the risk of developing asthma. Possible mechanisms are to induce the formation of regulatory T cells and to block the formation of specific antibodies. Food desensitization in children has been shown to be effective. Desensitization of children allergic to cow’s milk by oral administration of increasing doses of cow’s milk resulted in a significant increase in cow’s milk tolerance with no change in body IgE levels and a significant increase in IgG4 levels. It is important to note that the goal of oral immunotherapy is not complete tolerance to the previously allergic food, but rather to increase the tolerated dose and reduce or avoid severe adverse reactions. A wide variety of probiotics are thought to have a positive effect on maintaining the balance of intestinal flora, sustaining the intestinal microenvironment and restoring normal intestinal permeability. Probiotics can also enhance the immune barrier function of the intestinal tract and reduce the formation of pro-inflammatory factors, thus preventing the development of allergic inflammation. A recent study found that lactobacilli taken by pregnant women and infants up to 2 years of age reduced the risk of eczema by 50% at 2 years of age, suggesting a preventive effect on eczema. Further studies are needed to confirm the effect of probiotics on asthma. Several other pharmaceutical agents, including antihistamines, corticosteroids, and calcineurin inhibitors, have also been used to block the natural course of allergic diseases. One study showed that the prevalence of infants developing asthma did not change after 18 months of treatment with cetirizine, but reduced the risk of developing asthma in infants allergic to house dust mites and or pollen. Calcineurin inhibitors treat eczema by inhibiting the transcription of Th1- and Th2-like cytokines and by blocking T-cells activated by S. aureus superantigen. Future large-sample, multicenter, case-control studies are needed to clarify the safety of the above pharmacological agents and their effectiveness in interfering with the natural course of allergic diseases such as asthma.