Why does the upper eyelid swell?

Eyelid swelling is related to many factors. It may be caused by eyelid dermatitis, which is an allergic disease. It may require anti-allergic drugs, which are hormonal drugs. Being bitten by mosquitoes may also cause swelling and itching, and it may also require hormonal drugs. If the eyelids of one eye are red and swollen, and the pressure is positive, it may be considered related to the occurrence of sty, that is, bacterial infection of the eyelids, anti-inflammatory and anti-infective treatment is needed to eliminate infectious inflammation.