Allergic conjunctivitis in children is an IgE-mediated ocular inflammatory disease caused by allergens, mainly type I and IV hypersensitivity reactions, and is a non-infectious ocular surface disease in children. In recent years, the global incidence of allergic diseases is on the rise and has attracted more and more attention from the society. In Western countries, nearly 1/3 of children suffer from allergic diseases, and in Asian countries, a survey of children under 2 years old in Singapore in 2005 found that 42.2% of children had one or more allergic symptoms. As for allergic eye diseases, in the United States in 1988, the prevalence of seasonal allergic conjunctivitis alone was about 15%, and in 1993, the prevalence of allergic conjunctivitis was as high as about 25% according to Abelson et al. Many scholars at home and abroad have conducted epidemiological studies on allergic conjunctivitis. Allergic diseases are a systemic disease, and allergic conjunctivitis, allergic rhinitis, allergic dermatitis, and asthma are different clinical manifestations of this system, and studies have confirmed the correlation between allergic conjunctivitis and allergic rhinitis, asthma, and atopic dermatitis, and their treatment also has its commonality. Etiology (1) Allergic conjunctivitis: the child has an abnormal constitution and is particularly sensitive to certain irritants, as evidenced by a tendency for allergic or exudative lesions in the skin and mucous membranes; (2) Most scholars believe that allergic conjunctivitis may be a polygenic genetic disease. The presence of an immune responsegene (Ir gene) in the vicinity of the HLA region on chromosome 6 is also suggested. (3) Allergens: They can be divided into inhalation allergens (e.g. pollen, house dust, etc.), ingestion allergens (e.g. milk, fish and shrimp, etc.), contact allergens (e.g. dust mites, drugs, etc.), and inoculation allergens (e.g. vaccines, animal serum, etc.). (4) Seasonal and weather factors: Most patients have allergic symptoms in the allergic season, with May, June and September being the high season for allergy. (5) Other factors: such as mental stress, infection, cold stimulation can trigger the occurrence of allergic conjunctivitis or aggravate the symptoms. Symptoms: itchy eyes, lacrimation, photophobia, foreign body sensation, recurrent eye redness, morning mucous discharge, sneezing, runny nose, etc. The main symptoms are itchy eyes (99%-100%) and foreign body sensation (72%-80%), while infants and children have eye rubbing and lacrimation as the main complaints of parents. Cough and general discomfort are also the main complaints. Signs: In children with allergic conjunctivitis, conjunctival congestion, bulbar conjunctival edema, eyelid swelling, follicular and papillary hyperplasia, change in conjunctival color of the bulbar conjunctiva and dome, periocular cyanosis (dark circles), corneal rim colloid hyperplasia, and in severe cases, corneal epithelial infiltration and ulcer formation. The child also shows signs of nasal and skin allergy. Compared with allergic conjunctivitis in adults, allergic conjunctivitis in children is more clinically diagnostic in terms of edema and color changes of the bulbar conjunctiva and conjunctiva of the dome and the appearance of dark circles. There is an imbalance between the signs and symptoms of allergic conjunctivitis. Staging: Paying attention to and clarifying the staging of allergic reactions is the key to choosing a treatment plan. Allergic reactions are divided into early phase (after 15-60 min of allergen exposure) and late phase (after 2-6 h of allergen exposure). Generally, the more intense the allergic reaction is in the late phase, the more prominent the symptoms of allergic conjunctivitis are, and when patients come to the clinic, they are usually in the late phase. Diagnosis: An accurate diagnosis of allergy is important for the evidence-based treatment of patients and for potentially preventing or delaying the development of allergic disease. (1) A good clinical history includes a clear history of allergen exposure, or the onset of allergens in a specific environment, season, or climate, although not clear; a history of atopic dematitis (AD), atropic rhinoconjunctivitis (AR), or asthma and wheezing bronchitis is also helpful, especially for children with atypical AC. (2) Clinical manifestations such as itching, redness, tearing, photophobia, lid conjunctival papillae and follicles, and change in the color of the bulbar conjunctiva. (3) Anti-allergic treatment is effective. (4) Eosinophils are significantly increased on cytologic examination if necessary, but Abelson pointed out that the absence of eosinophils in the smear does not exclude allergic conjunctivitis because the cells are located deep in the conjunctiva, and Bonini et al. also found that allergic reactions are more severe in the conjunctival stroma, and that positive results of skin tests, radioallergen adsorption tests, and enzyme immunoassays for serum IgE levels are helpful. The diagnosis of allergic conjunctivitis.