The patient woke up with one eye swollen, it may be caused by improper sleeping position, but also may be caused by blepharitis, conjunctivitis and other diseases. 1. Improper sleep position: If the patient sleeps in a side-lying position all the time, compressing one eye, the patient may have unilateral eye edema, which generally does not require special treatment. 2. Blepharitis: Blepharitis is an acute purulent inflammatory lesion that occurs in the glands of the eyelids, mainly caused by staphylococcal infections, and patients may experience redness and swelling of the eyelids. If the patient does not remove the eye makeup before going to bed or rubbing the eyes with hands, it may cause blepharitis, so the patient may have redness, swelling, pain and other uncomfortable symptoms in one eye. 3. Conjunctivitis: Conjunctivitis patients in the inflammation stimulation, can also appear in the eyes red, swollen, itching and increased secretion and other discomforts. If the patient does not pay attention to personal hygiene, wipe the eyes with hands before going to bed or wear contact lenses for a long time, there may be a waking up one eye swollen situation. Patients with swelling in one eye are advised to seek medical attention to assess their condition and follow medical advice.