Bloodshot eyes may be caused by physiological reasons, or may be caused by conjunctivitis, keratitis, glaucoma and other pathological reasons. 1. Physiological causes: Staying up late without resting the eyes, using the eyes for a long time without interruption and other behaviors can lead to physiological causes of eye congestion, which need to ensure that the eyes get enough rest. 2. Conjunctivitis: Inflammation of the conjunctiva due to bacterial infection can lead to conjunctival congestion. 3. Keratitis: Infection of the cornea by bacteria or viruses may cause inflammation, resulting in congestion of the eyes. 4. Glaucoma: acute attack of glaucoma, when the intraocular pressure rises, it can also lead to ciliary congestion, and in severe cases, it can also lead to conjunctival congestion. There are many causes of eye congestion. If the congestion cannot be relieved by rest or is accompanied by eye discomfort, patients are advised to go to the hospital as soon as possible.