Atopic dermatitis is one of the common diseases in dermatology and has a significant impact on the quality of life of patients. The prevalence of atopic dermatitis in China has been gradually increasing over the past 20 years. Atopic dermatitis (AD) is a chronic, relapsing, inflammatory skin disease that is often associated with intense itching and has a serious impact on quality of life. The disease usually begins in infancy and accounts for about 50% of all patients before the age of 1. The disease has a chronic course and can extend into adulthood in some patients, but there are also adult-onset patients. In developed countries, the prevalence of this disease in children can be as high as 10-20%. In China, the prevalence of atopic dermatitis has been gradually increasing over the past 20 years, with a total prevalence of 0.70% among school-age adolescents (6-20 years old) in 1998, 2.78% among preschool children (1-7 years old) in 2002,10 and 8.3% among children aged 3-6 years (8.5% for males and 8.2% for females) in the 2012 Shanghai Regional Epidemiological Survey. The prevalence rate was significantly higher in urban than in rural areas (10.2% compared to 4.6%). 1. Etiology and pathogenesis The development of atopic dermatitis is closely related to genetic and environmental factors. Family members with a history of allergic diseases, such as parents, are significantly more likely to develop the disease, and genetic factors mainly affect skin barrier function and immune balance. Environmental factors include environmental changes, lifestyle changes, excessive washing, infectious agents and allergens. In addition, psychological factors (e.g., stress, anxiety, depression, etc.) also play a role in the development of atopic dermatitis. The exact pathogenesis of atopic dermatitis is not known. It is generally believed to be based on genetic factors, due to allergen entry and microbial colonization (e.g., Staphylococcus aureus and Malassezia), resulting in an abnormal immune response and inflammation of the skin, triggering rash and pruritus, which can be further aggravated by adverse stimuli such as scratching and excessive washing. The abnormal immune response in atopic dermatitis involves multiple components, such as allergen presentation by Langerhans cells and skin dendritic cells, abnormal Th2-dominated immune response, regulatory T cell dysfunction, IgE overproduction, and elevated eosinophils. In addition, the production of cytokines and inflammatory mediators by keratinocytes is also involved in the inflammatory response. Non-immune factors such as abnormal neuroendocrine factors can also be involved in the development of skin inflammation. The clinical manifestations of atopic dermatitis are varied, but the most basic features are dry skin, chronic eczema-like dermatitis and intense pruritus. The vast majority of this disease begins in infancy and childhood, and some can occur in childhood and adulthood. According to the different age groups: 1, infancy (birth to 2 years) manifested as infantile eczema, mostly on both cheeks, forehead and scalp, the rash can be dry or oozing. Childhood (2 to 12 years old): Mostly evolved from infancy, but also may not occur after infancy. The rash tends to be dry and hypertrophic, with obvious moss-like changes. 2, young people and adults (12 years old and above) lesions are similar to those of children, also mainly subacute and chronic dermatitis, mainly in the elbow fossa, rouge fossa, the front of the neck and other parts, but also in the trunk, limbs, face, back of the hands, most of the dry, hypertrophic dermatitis damage, some patients can also be manifested as itchy rash-like rash. Patients with atopic dermatitis have a number of characteristic manifestations that help in the diagnosis of the disease, including dry skin, ichthyosis, periorbital keratosis, palmaris, eyelid eczema, hand eczema, nipple eczema, discoid eczema, sweat pimples, labyrinthitis, recurrent conjunctivitis, infraorbital folds, periorbital dark halo, pale face, anterior cervical folds, eczema in the subnasal and ear folds, white skin scratching, pruritus during sweating, and sensitivity to wool. In addition, some patients also have other atopic diseases at the same time, such as allergic asthma and allergic rhinitis, and some have significant allergic protein allergies, such as allergy to some food proteins (meat, eggs, milk, nuts, etc.) or inhalants (dust mites, house dust mites, etc.). All these features are of great value in the diagnosis of atopic diseases. About 40% to 80% of patients have a family history of allergy, such as atopic dermatitis, allergic asthma, allergic rhinitis, allergic conjunctivitis, etc. in the family. The family history is very important for the diagnosis of atopic dermatitis. Some patients, especially those with severe atopic dermatitis, may have elevated total serum IgE, and about 40% to 60% of patients have elevated peripheral blood eosinophils, which often correlate with the activity of the disease and can rapidly return to normal with effective treatment. Atopic dermatitis can be divided into simple type, which is characterized by dermatitis only, and mixed type, which is combined with allergic asthma, allergic rhinitis and allergic conjunctivitis. The exogenous type has elevated total serum IgE levels, elevated specific IgE levels, and elevated peripheral blood eosinophils, whereas the endogenous type does not have significant or absent changes as described above. The endogenous form of atopic dermatitis is easily missed and should be taken seriously.