Swelling of one eye in nephritis patients may be caused by hypoproteinemia, decreased glomerular filtration rate and loose eyelid tissue. 1. Hypoproteinemia: patients with nephritis usually have proteinuria, which causes hypoproteinemia. Decrease in plasma colloid osmotic pressure will make the water inside the blood vessel reach the outside of the blood vessel, which will cause the manifestation of edema. 2. Decreased glomerular filtration rate: patients with nephritis often combined with decreased glomerular filtration rate, that is, although the reabsorption function of the renal tubules is normal, but due to the decrease in the glomerular filtration fraction, resulting in a decrease in the amount of water filtered out and a relative increase in the amount of water reabsorbed, resulting in an imbalance of the glomerular tubes, causing sodium retention, which causes the accumulation of water in the body, resulting in the manifestation of edema. 3. Eyelid tissue relaxation: edema is one of the prominent symptoms of nephritis patients, night sleep position lying down, it is easier to make the excess fluid accumulation in the thin skin such as eyelids, and edema, and mostly in the morning, can be alleviated with activities. In conclusion, nephritis causes eye swelling for many reasons, but because nephritis is a systemic disease, the symptoms of eyelid edema appear symmetrically, if nephritis is swollen in one eye, it is recommended that the patient pay attention to rest, go to the hospital in a timely manner, and after completing the relevant examinations, symptomatic treatment is carried out under the guidance of the doctor.