A bloodshot eye is caused by the dilation or swelling of tiny blood vessels on the surface of the eye. This can happen for various reasons, both minor and serious. Common causes include irritation or inflammation from allergies, dryness, infections like conjunctivitis (pink eye), contact lens wear, exposure to irritants such as smoke or chemicals, lack of sleep, and eye strain. More severe causes may include eye injuries, burst blood vessels (subconjunctival hemorrhage), iritis (inflammation of the iris), uveitis, glaucoma, or autoimmune disorders affecting the eyes. Lifestyle factors such as alcohol use and drug misuse can also contribute to the condition. In many cases, bloodshot eyes improve on their own, but some underlying causes may require medical attention.
