A swollen upper eyelid and a little bit of pain may be caused by a granuloma, bacterial conjunctivitis, mosquito bites, etc. The most important thing to remember is that it’s not just a swollen eyelid, it’s also a sore eyelid. 1. Wheat grain swelling: the upper eyelid of the eye is swollen and a little pain may be caused by wheat grain swelling, wheat grain swelling, also known as blepharitis, usually staphylococcal infections caused by the main manifestations of eyelid redness and swelling, tenderness, pain in the blink of an eye is more pronounced. 2. Bacterial conjunctivitis: swollen upper eyelids and a bit of pain may be caused by bacterial conjunctivitis. Bacterial conjunctivitis can jeopardize vision, clinical manifestations of foreign body sensation in the eye, burning sensation, itching, sticky purulent discharge, conjunctival congestion, tearing, eyelid swelling and pain. 3. Mosquito bites: swollen upper eyelid and a little pain may be caused by mosquito bites, mosquitoes if the bite of the upper eyelid, mosquito saliva in the acidic substances will stimulate the upper eyelid, triggering allergies and produce redness, itching, pain and other symptoms. Patients with swollen upper eyelids and a little pain, accompanied by other symptoms, it is recommended to go to the hospital, under the guidance of the doctor to clarify the cause of the disease and then treatment.