Swollen lower eyelids in children may be caused by drinking too much water or diseases such as insect bite dermatitis or blepharitis. 1. Drinking too much water: If a child drinks a lot of water before going to bed, or cries before going to bed, it will lead to ocular edema, which will result in the swelling of the lower eyelids. 2. Insect bite dermatitis: Insect bite reaction is an allergic reaction to insect bites, manifested by skin lesions on the bitten skin, often accompanied by itching. If a child’s lower eyelid is bitten by an insect, localized changes such as redness, erythema, and blisters will occur, resulting in swelling of the child’s lower eyelid. 3. Blepharitis: It is an acute purulent inflammatory lesion that occurs in the eyelid glands, mainly caused by staphylococcal infections, and secondly, it is also related to eye rubbing and poor eye hygiene. The patient’s typical manifestations are redness, swelling, heat and pain in the affected area, and the condition develops rapidly, which can be manifested as soft boils and pustules, usually infecting one eye, and can occur on both the upper and lower lids. There are many causes of lower eyelid swelling in children. If accompanied by other uncomfortable symptoms, parents are advised to bring their children to the doctor for relevant examinations to clarify the cause.