If the upper eyelid swelling on one side is not painful or itchy, the first consideration is that it is caused by a local factor in the eye. If the swelling is systemic, which usually occurs in both eyes at the same time, the swelling of one side of the upper eyelid is considered to be a lid gland cyst. A lid gland cyst is a localized nodule caused by a blockage of the glandular ducts. There is no obvious specific discomfort, and the area shows eye redness, eye pain and localized nodules with whiteheads, etc. In this case, localized eye drops need to be given, and appropriate minor surgery to remove the cyst can also be done at the hospital.