Inflammation of the surface of the eye (conjunctivitis) and inflammation of the eyelids (blepharitis) are common causes of swollen eyes. Other common causes include crying, lack of sleep, or excessive rubbing of the eyes. Wearing contact lenses can also result in eye swelling. Depending on the cause, swelling may occur in one or both eyes, and it may be accompanied by redness, pain, itching, excessive tear production, or other types of discharge from the affected eyes.