Redness and swelling of the lower eyelids of small children may be caused by mosquito bites, blepharitis, bacterial conjunctivitis and other causes. 1. Mosquito bites: If a child’s lower eyelid is bitten by a mosquito, an allergic reaction may occur, and the child may have redness and swelling of the lower eyelid, accompanied by itching of the eyelid. 2. Blepharitis: The redness and swelling of a child’s lower eyelids can also be caused by blepharitis, in which inflammation stimulates the child to develop limited redness, swelling and pain of the eyelid skin. 3. Bacterial conjunctivitis: The redness and swelling of a child’s lower eyelid can also be caused by bacterial conjunctivitis, in which the child may experience eyelid swelling, foreign body sensation, burning sensation, itching, tearing and other discomforts, which may also be accompanied by viscous purulent secretion. It is recommended that patients with significant eyelid redness and swelling seek prompt medical attention to evaluate their condition and treat them under the guidance of a physician.