Having bloodshot eyes while fighting off a sickness, like a cold or the flu, is a common physical manifestation of the body’s internal fight against infection. Medically known as conjunctival injection, this redness occurs when the tiny blood vessels on the surface of the eye, specifically those in the conjunctiva, swell and become highly visible. This symptom is often a direct and temporary side effect of your immune system activating to restore health. Understanding the biological connection between a systemic illness and your eyes can help demystify this uncomfortable symptom.
The Systemic Link Between Illness and Eye Redness
The underlying cause of bloodshot eyes during an illness is the body’s generalized inflammatory response. When a virus or bacteria invades, the immune system releases signaling molecules, such as pro-inflammatory cytokines, throughout the bloodstream to rally a defense. These molecules increase blood flow and permeability in affected areas, helping immune cells reach the site of infection.
This systemic process affects the delicate vasculature of the eyes, causing the small blood vessels covering the white part of the eye to dilate and fill with blood. The resulting congestion creates the visible bloodshot or red appearance. The eyes are mirroring the widespread inflammatory state present in the body as it works to fight the illness.
Dehydration, which frequently accompanies a systemic sickness like fever or flu, also contributes significantly to eye redness. When the body lacks sufficient fluid, tear production is reduced, leading to dryness and irritation on the eye’s surface. This lack of lubrication causes the conjunctiva to become easily inflamed, often exacerbating the visible redness already present from the immune response.
Common Sicknesses That Trigger Bloodshot Eyes
Many common ailments that trigger a systemic immune response can cause bloodshot eyes. Viral upper respiratory infections, such as the common cold or influenza, are frequent culprits because they initiate a widespread inflammatory cascade. In some cases, these viral infections can also lead to secondary viral conjunctivitis, where the virus directly infects the surface of the eye.
Sinus infections cause redness through systemic inflammation and increased pressure. Congestion in the nasal cavities and sinuses can put pressure on surrounding structures, sometimes impeding the drainage of blood from the veins around the eyes. The physical strain from constant sneezing or forceful coughing may also cause a small blood vessel on the eye surface to burst, resulting in a bright red, localized patch known as a subconjunctival hemorrhage.
Illnesses that cause a high fever or persistent vomiting lead to pronounced dehydration, worsening the eye’s condition. Fluid loss reduces the moisture available for tear film maintenance, leaving the eyes dry, gritty, and more susceptible to irritation and redness.
Immediate Relief and Home Management Strategies
For mild bloodshot eyes associated with a common sickness, several simple strategies can help manage the discomfort. Over-the-counter lubricating eye drops, often called artificial tears, are a primary option to combat dryness caused by fever and dehydration. These drops help restore the moisture film on the eye surface, reducing irritation and redness.
Applying a clean, cool compress to the closed eyelids for a few minutes can provide soothing relief by constricting the dilated blood vessels. Avoid using eye drops advertised as “redness-relievers” for prolonged periods. These contain vasoconstrictors that can cause a rebound effect, potentially worsening the redness once discontinued.
Systemic hydration is necessary for home management, as it addresses the underlying dehydration contributing to the symptom. Consuming plenty of water, clear broth, and electrolyte-containing fluids supports recovery and promotes better tear quality. Also, refrain from rubbing your eyes, as this introduces irritants and can further damage inflamed blood vessels.
Warning Signs That Require a Doctor Visit
While bloodshot eyes are often a harmless byproduct of fighting an illness, certain accompanying symptoms suggest a more serious underlying eye condition that requires professional attention. Consult a healthcare provider if the redness is accompanied by severe pain or an unusual sensitivity to light (photophobia). These symptoms can indicate a deeper inflammation or a more significant infection within the eye structure.
Any sudden change in vision, such as blurriness, cloudiness, or a noticeable loss of sight, should be considered a medical urgency. The presence of thick, colored discharge, specifically yellow or green, strongly suggests a bacterial infection, which typically requires prescription antibiotic eye drops to resolve.
If the redness and irritation are confined to only one eye, or if the symptoms do not begin to improve within a few days after the primary illness subsides, a medical evaluation is warranted. Redness that persists for over a week, or that is accompanied by the feeling of a foreign object stuck in the eye, indicates that the issue may be a distinct ocular problem rather than a simple side effect of a cold or flu.