A swollen eyelid is caused by the fluid buildup or inflammation in the delicate tissues around the eye. Common causes include allergies, styes and chalazia, infections, and other triggers like injury, bug bites, lack of sleep, or crying.
It can be treated with cold compresses, warm compresses, over-the-counter antihistamine drops or oral antihistamines for allergies, antibiotic drops or ointments for bacterial infections, and eyelid hygiene.
See the doctor immediately if you have worsening symptoms like severe pain, vision changes, and inability to move the eye normally.