Allergic conjunctivitis is a condition in which the conjunctival tissue of the eye comes into contact with an allergen, causing an allergic reaction in the conjunctiva, resulting in the release of allergenic factors such as histamine from conjunctival mast cells, which in turn causes local capillary dilation, resulting in symptoms such as redness, swelling and itching in the eye. The most common allergen causing allergic conjunctivitis is plant pollen, and the symptoms of this allergic conjunctivitis tend to vary seasonally. Seasonal allergic conjunctivitis is most common in young and middle-aged people and has a rapid onset, often accompanied by allergic rhinitis, so patients often have symptoms such as sneezing, runny nose and sore throat, so many people think they have a “cold”. The main symptom of allergic conjunctivitis is unbearable itchiness. More than 90% of patients with allergic conjunctivitis have symptoms of itchy eyes, in addition to conjunctival congestion, edema, and redness of the eyelid skin, etc. Patients usually do not have eye pain or significant visual impairment. Allergic conjunctivitis tends to have very little ocular discharge, which is the main point of differentiation from bacterial conjunctivitis, so treatment is not based on the use of antibiotic eye drops. Identification and removal of allergens is the key to treatment and prevention. For example, for pollen allergy, minimize outdoor activities during pollen-rich seasons, or use goggles and wear a more protective mask when going outside. However, most allergic conjunctivitis does not necessarily identify the exact allergen, or the allergen type is complex and not easily identified, which is the fundamental reason why allergic conjunctivitis is recurrent and not easily cured. If you can’t identify the allergen for a while, then, first of all, you should improve your living environment, especially the air quality or indoor temperature, so that the impact of the allergen can be reduced. Secondly, it is important to pay attention to nutrition and exercise, regularity of life and rest to enhance physical fitness and restore the normal state of the immune system. The treatment of allergic conjunctivitis is based on local medication. Local antihistamine eye drops can play a rapid role in relieving itching, while mast cell stabilizer – sodium cromoglycate eye drops, which can both treat and prevent allergic conjunctivitis, is also a more commonly used drug. Glucocorticoid eye drops are effective and fast-acting, but they should be used with caution under the guidance of a doctor because of their side effects. In addition, those with other organ allergies should be treated with systemic medication as appropriate.