The causes of congestion in one eye and congestion in both eyes are basically the same and can be summarized as eye congestion. The causes of eye congestion are usually inflammatory reactions, trauma, or elevated intraocular pressure and transient irritation can occur, and it is recommended to do a systematic eye examination to clarify the cause. Common causes: 1. Inflammatory reaction: Infections and allergies can cause local inflammatory reactions, causing eye congestion, and when there is an inflammatory reaction there will be a large amount of secretions in the eye, affecting the normal state of the eye itself, causing local vasodilation of the conjunctiva and congestion in one eye; 2. Trauma: When trauma occurs in the eye, such as contusion, impact injury, mechanical injury, etc., it may cause local vasodilation of the conjunctiva or rupture, leading to congestion in one eye; 3, elevated intraocular pressure: glaucoma, intraorbital occupancy, ocular tumors and hypertension, etc., may cause elevated intraocular pressure, impaired blood circulation or capillary rupture and bleeding, leading to congestion in one eye; 4, transient irritation: such as sudden exposure to sand, dust, body wash, airflow, smoke, etc., may also cause transient congestion in one eye, which is caused by irritating substances caused by irritating substances entering the eye. Treatment: Generally, eye congestion caused by transient irritation can often subside on its own, while congestion in one eye caused by other aspects can be eliminated with some antibacterial and anti-inflammatory drugs to eliminate infectious factors. If bleeding occurs after congestion in one eye, the bleeding should be promptly suppressed with anticoagulant drugs. On the other hand, for diseases that cause more serious bleeding, the primary disease should be treated.