Swollen eyelids for no reason can be caused by allergies, mosquito bites, blepharitis and other reasons. 1. Allergy: If you come into contact with allergens in your normal life, such as pollen, willow flakes, dust and so on. When the allergens stimulate the human body localized allergic reaction, there may be no reason eyelid swelling. 2. Mosquito bites: If the eyelid area is unknowingly bitten by mosquitoes, it may lead to the phenomenon of swollen eyelids for no reason, usually manifested as a transparent watery state, and accompanied by localized itching. 3. Blepharitis: If the glands of the eyelids are infected by bacteria, causing suppurative inflammation, the eyelids may be swollen for no reason and pain and other symptoms. If you have a swollen eyelid for no reason, you should go to a regular hospital in time to find out the cause of the problem and take targeted treatment under the guidance of a professional doctor.