Redness and swelling of the lower eyelids of one and a half year old babies may be related to allergic reactions, or may be caused by blepharitis, mosquito bites and other reasons. 1. Allergic reaction: commonly found in allergic babies, after eye contact with pollen, dust mites and other substances, it is likely to cause an allergic reaction in the eyelids, which may cause redness and swelling of the eyelids of the affected children, and may be accompanied by obvious itching and other uncomfortable symptoms. 2. Blepharitis: If a one-and-a-half-year-old baby often rubs his eyes with dirty hands, it is easy to cause the eyelid glands to be infected by pathogenic bacteria, causing blepharitis, which may also cause redness and swelling of the lower eyelids, and the child may also be accompanied by eyelid pain, tearing and other symptoms. 3. Mosquito bites: In summer, when mosquitoes are abundant, if the child is not well protected and the eyelid is bitten by mosquitoes, the child may have redness and swelling of the eyelid, which may be accompanied by itching, stinging and other uncomfortable symptoms. It is recommended that children with significant redness and swelling of the eyelids seek prompt medical attention to assess their condition and follow medical advice.