A common cold, a viral upper respiratory infection, can cause red eyes. This redness arises from two mechanisms. Sometimes, it is a secondary effect caused by inflammation and congestion within the facial passages, which is generally transient and mild. In other instances, the cold virus itself can directly infect the eye’s surface, leading to a more noticeable and highly contagious condition. Understanding the difference between these two causes is important for proper management and hygiene.
The Inflammatory Link Between Colds and Red Eyes
The most common reason for eye redness during a cold relates to the interconnected anatomy of the face. The tear drainage system, or nasolacrimal duct, links the eye directly to the nasal cavity, draining tears and keeping the eye clean.
When a cold virus causes inflammation and swelling in the nasal passages and sinuses, the lining of the nasolacrimal duct also becomes inflamed. This swelling narrows or blocks the duct, preventing tears from draining properly into the nose. The resulting backup of tears, known as epiphora, leads to watery, irritated eyes.
Congestion also increases internal pressure within the sinuses, which are located near the eyes. This pressure can cause the tiny blood vessels on the conjunctiva to dilate. When these vessels swell, they become more visible, resulting in a bloodshot appearance. This redness is mild and resolves naturally as the nasal and sinus congestion clears up.
Distinguishing Viral Conjunctivitis (Pink Eye)
A more direct cause of red eyes during a cold is viral conjunctivitis, commonly known as pink eye. This condition occurs when cold viruses, frequently adenoviruses, spread to the conjunctiva, the thin, clear membrane covering the white part of the eye. The virus typically travels from the respiratory system to the eye through hand-to-eye contact after touching contaminated surfaces or tissues.
Viral conjunctivitis produces a more intense redness than simple congestion-related irritation. It is often accompanied by a distinct gritty feeling, a persistent, clear, watery discharge, and increased sensitivity to light.
This infection is highly contagious and often begins in one eye before spreading to the other within a few days. Since viral conjunctivitis is caused by a virus, it cannot be treated with antibiotics and must run its course, typically taking one to two weeks. Proper hand hygiene is important to prevent the virus from spreading to other people.
Managing Symptoms and Knowing When to Seek Care
For mild redness caused by congestion or typical viral conjunctivitis, several measures can provide comfort. Applying a clean, cool compress to the closed eyes several times a day helps reduce swelling and irritation. Using over-the-counter lubricating eye drops, often called artificial tears, can help wash away irritants and soothe the eye’s surface. Frequent and thorough handwashing is the most effective action to prevent the spread of the virus to the other eye or to other people.
It is necessary to seek professional medical attention if the red eye symptoms suggest a more severe issue. Warning signs that necessitate a medical evaluation include severe pain in the eye or around the orbit. Any noticeable change in vision, such as blurring or difficulty seeing clearly, should be immediately addressed.
The presence of a thick, yellow, or greenish discharge, especially if the eyelids are stuck together upon waking, could indicate a secondary bacterial infection. If the redness or irritation lasts longer than seven to ten days, a healthcare provider should be consulted for an accurate diagnosis.