Swelling of the upper eyelid of one eye that occurs when you first wake up in the morning is considered to be due to puffiness caused by staying up late, poor sleep quality, or drinking water before bedtime, usually without obvious symptoms such as swelling or pain, and can subside on its own within a period of time. In addition, the following conditions can also cause swelling in the upper eyelid of one eye: 1. Blepharitis: commonly known as wheals, usually caused by a bacterial infection, occurs in the upper or lower eyelid of one eye. The main manifestation is a soft boil or pustule accompanied by redness, swelling, and pain, causing the patient’s upper eyelid to swell. In the early stage, the symptoms can be treated and relieved by keeping the eye area clean, applying hot compresses, drops of levofloxacin eye drops, and applying tobramycin eye ointment. 2. Allergy: It may be related to a variety of allergens such as dust mites, mosquito bites, pollen, mangoes, seafood, etc. Long-term contact lens wear can cause giant papillary conjunctivitis, and all of the above may cause allergic swelling in one or both eyes of the patient, and patients are advised to first clarify the allergens It is recommended that patients first identify the allergens and then follow medical advice for active anti-allergic treatment; 3. Folliculitis: It occurs on the head and face, so it can appear on the upper eyelid and cause swelling of the upper eyelid. The main causes may be related to a variety of factors such as incomplete cosmetic cleaning and upper eyelid trauma. Mild folliculitis can subside on its own, while patients should maintain local cleanliness and apply mupirocin ointment, erythromycin ointment, and other medications under medical supervision. 4. Chalazion: The main manifestation is a tough eyelid lump, which may be asymptomatic when the lesion is small, but the lump gradually becomes larger and can affect vision, with a few patients showing redness and pain. In the early stage, hot compresses can be applied. If the condition cannot be relieved, prompt consultation should be made for glucocorticoid injection therapy or surgery, which generally has a better prognosis; 5. Other aspects: eye diseases such as inflammation of the lacrimal gland, intraorbital cysts, conjunctivitis or inflammatory pseudotumor, or conditions such as thyroid and kidney diseases may cause swelling of the upper eyelid of one eye. If the patient cannot be relieved by rest, hot compresses, etc., and there is obvious pain, redness and swelling and other conditions that worsen, he or she should immediately seek medical attention.