One eye is swollen and the other eye is normal, which is commonly caused by bad sleeping habits, eyelid skin allergy, rubbing the eyes, inflammation of the oral and maxillofacial region, and so on. 1. Bad sleeping habits: for example, drinking too much water before going to bed or sleeping with the head positioned too low or to one side habitually, which can easily lead to puffy eyes. 2. Eyelid skin allergies: Eyelid skin allergic reactions caused by mosquito bites or contact with external allergens can lead to eyelid swelling. 3. Rubbing the eyes: Rubbing the eyes can lead to edema in the local tissues of the eyes, which is manifested as puffy eyelids. 4. Inflammation of the oral and maxillofacial region: Inflammation of the oral and maxillofacial region may involve the eyes upstream and cause edema. One eye is swollen, the other eye is normal, long time no relief or accompanied by other discomforts, it is recommended that the patient consult a doctor in a timely manner to clarify the cause of the disease, targeted treatment.