What Causes Red Blood Vessels in the Eyes?

The general concept of “eye redness” refers to a reddish appearance of the sclera (the white part of the eye). This occurs when blood vessels in the bulbar conjunctiva and sclera become dilated, congested, or hemorrhagic under certain conditions. Because different ocular tissues receive blood supply from distinct vascular sources, the patterns of redness vary—and these variations often reflect involvement of different anatomical structures or pathological processes. So, what causes visible “bloodshot eyes” or “red veins” in the eyes? Below, we address this question.

What Causes Red Veins in the Eyes?

1. Excess Liver Fire

A prominent appearance of red veins in the eyes may stem from excessive liver fire. The liver and eyes are closely interrelated in traditional Chinese medicine. When liver function declines, it may lead to stagnation of liver qi and excess liver fire. Symptoms of excessive liver fire often include ocular discomfort—such as dryness, pain, and diffuse redness across the sclera.

2. Eye Strain

Red veins in the eyes are frequently associated with prolonged visual tasks. For instance, individuals who spend extended periods working at a computer without adequate rest may develop numerous visible blood vessels in the conjunctiva. Therefore, it is essential to practice moderation during visual activities—taking regular breaks to close the eyes and relax—to prevent excessive ocular fatigue and related symptoms.

3. Conjunctivitis

Diffuse red veins in the eyes may indicate conjunctivitis—particularly allergic conjunctivitis. Exposure to irritants or allergens can trigger intense itching, which in turn leads to marked conjunctival hyperemia (increased blood flow) and visible redness. If conjunctivitis is the underlying cause, prompt treatment—including topical ophthalmic medications (e.g., antihistamine or anti-inflammatory eye drops) and/or systemic therapy—is recommended.

4. Sleep Deprivation

Chronic sleep deprivation—especially frequent late-night activity—can cause engorgement of the conjunctival blood vessels, resulting in visible red veins. Moreover, prolonged sleep loss may deplete the body’s resources and further exacerbate liver fire. Individuals affected should minimize overnight activity and ensure sufficient, high-quality sleep daily; only adequate rest can nourish the eyes and help prevent conjunctival redness.

Above are the primary causes of red veins in the eyes. We hope this information proves helpful.