Very red eyes with a lot of blood can be caused by congestion of the conjunctiva and blood vessels of the eye, and is considered to be related to physical or chemical irritation, eye fatigue, conjunctivitis or keratitis. 1. The eye enters into foreign objects such as dust, eyelashes or certain chemicals, due to the friction of foreign objects and conjunctival irritation, which can cause conjunctival congestion and redness of the eye. Stay up late, visual fatigue, etc., the conjunctiva will also be congested, red blood, but usually can be relieved after sufficient rest. 2. Conjunctivitis: Conjunctivitis caused by pathogenic microorganisms, allergies, etc., with conjunctival congestion, redness, itching, pain and increased secretion. 3. Keratitis: The cornea is susceptible to infection and trauma, and keratitis occurs with a rapid onset, causing severe pain, photophobia and other symptoms of eye irritation and ciliary congestion. Red eyes, red blood or eye pain and other symptoms should be timely medical care, complete eye examination, identify the cause of the targeted treatment.