Red eye is a common but potentially serious condition that can range from mild irritation to severe infections requiring immediate medical attention. Eye redness occurs when blood vessels in the eye become dilated or inflamed, often accompanied by pain, discharge, or vision changes. While some cases of red eye may be due to minor irritation or allergies, persistent or severe symptoms can indicate serious conditions such as bacterial infections, corneal ulcers, glaucoma, or other sight-threatening issues that need urgent medical evaluation.