Watery eyes during a cold, flu, or sinus infection are mostly the work of a reflex arc that links the lining of your nose to your tear glands. When the nasal mucosa becomes inflamed and swollen, nerve signals travel from the nose to the brain and then back out to the lacrimal glands above each eye, telling them to ramp up tear production. This reflex is one of several overlapping mechanisms, and the picture gets more interesting when you consider that some respiratory viruses can target the eyes directly.
How Your Nose Talks to Your Tear Glands
The inside of your nose is packed with sensory nerve endings, particularly a type called C-fiber nociceptors. These are the same nerves that detect irritants like pepper spray or strong fumes, and during an infection they respond to the swelling, mucus buildup, and chemical irritants that inflammation produces. When these nerves fire, they send signals along afferent pathways up to the brainstem. The brainstem then relays signals back out through a different set of nerves, the parasympathetic (cholinergic) efferent fibers. One branch of that outgoing signal heads to the nasal glands themselves, which is why your nose runs. But another branch reaches the lacrimal glands, stimulating them to secrete tears.
This nasonasal reflex, as researchers call it, is the main reason your eyes water when you have a stuffy, inflamed nose. The nasal afferent triggers stimulate the lacrimal glands even though nothing is directly irritating your eyes.1PubMed. Nasonasal reflexes, the nasal cycle, and sneeze It is the same basic wiring that makes your eyes tear up when you inhale something pungent like horseradish or ammonia. During a cold or sinus infection, the inflammatory soup in your nasal passages keeps those C-fiber receptors firing for days, so the tear-producing reflex stays chronically activated rather than flaring for a moment and settling down.
This also explains why treating nasal congestion often helps the watery eyes too. Anticholinergic nasal sprays, which block the cholinergic efferent limb of the reflex, reduce both the runny nose and, to some extent, the reflexive tearing. Decongestants that shrink swollen nasal tissue lower the stimulus at the source. When people say their eyes stopped watering after they finally cleared their sinuses, the reflex connection is the reason.
When Respiratory Viruses Target the Eyes Directly
The reflex arc accounts for most of the everyday tearing during a cold, but it is not the whole story. Some respiratory viruses have a genuine tropism for ocular tissue, meaning they can infect the cells of the eye itself. Certain adenoviruses and influenza strains are well-documented culprits, but documented ocular disease has been reported with essentially all of the major respiratory viruses.2PubMed Central. Ocular tropism of respiratory viruses When a virus sets up in the conjunctiva (the thin membrane covering the white of the eye and inner eyelids), it triggers a local inflammatory response that produces extra tears, redness, and sometimes a gritty or burning sensation.
This is why some colds and flu episodes come with more eye involvement than others. A rhinovirus that stays largely in the nasal passages will produce reflex tearing but leave the eyes themselves feeling fine. An adenovirus infection, on the other hand, may cause full-blown viral conjunctivitis with pink, swollen, streaming eyes that feel irritated on their own, independent of nasal congestion. The virus can reach the eye through direct contact (touching your nose and then your eye), through the nasolacrimal duct that connects the nasal cavity to the eye, or even through aerosolized droplets landing on the conjunctival surface.
This matters practically because the two situations call for different responses. Reflex tearing from nasal congestion is annoying but harmless to the eye and resolves when the congestion clears. Direct viral infection of the eye can occasionally cause complications like corneal involvement or secondary bacterial infection, and it is also highly contagious through hand-to-eye contact and shared towels. If your eyes are not just watery but also red, sticky, or painful, the virus may have moved beyond the nose.
The Role of Systemic Inflammation
Beyond the direct nerve reflex and direct viral infection, there is a third contributor that is easy to overlook: your immune system’s systemic inflammatory response. When you are fighting off an infection, your body releases a cascade of inflammatory mediators, including histamine, prostaglandins, and various cytokines. These molecules circulate throughout the body and affect mucous membranes everywhere, not just in the nose. The conjunctiva of the eye is a mucous membrane, and it responds to elevated histamine and inflammatory signaling by becoming more permeable and producing more fluid.
This is part of why people with the flu, who tend to have a stronger systemic inflammatory response than those with a common cold, often report more pronounced eye watering and eye discomfort. The whole-body immune activation creates a background level of mucosal irritation that adds to whatever the nasal reflex is already doing. It is also why antihistamines, which most people think of as allergy drugs, can reduce watery eyes during a cold. They are not treating an allergic reaction; they are dampening one of the inflammatory mediators that contributes to tearing.
Fever compounds the picture. Elevated body temperature increases evaporation from the surface of the eye, which the lacrimal glands try to compensate for by producing more tears. At the same time, fever tends to make the blood vessels in the conjunctiva dilate, which increases fluid leakage into the tear film. So a feverish illness hits you from multiple angles: the nasal reflex is firing, systemic inflammation is irritating the conjunctiva, and the fever itself is altering tear dynamics.
Why Sinus Infections Are Especially Bad
If you have ever had a sinus infection, you probably noticed that the watery eyes were worse than during a typical cold. There is a straightforward anatomical reason for this. The sinuses sit in close proximity to the orbits (the bony cavities housing the eyes), and the maxillary and ethmoid sinuses in particular share thin bony walls with the orbit. When these sinuses become inflamed and filled with infected mucus, the pressure and swelling can compress or irritate the nasolacrimal duct, the tiny channel that normally drains tears from the eye down into the nasal cavity.
Under normal circumstances, your lacrimal glands produce tears continuously and the nasolacrimal duct carries the excess away. This is actually why your nose runs when you cry: the excess tears drain through the duct into the nose. During a sinus infection, swelling around the duct can partially or fully block that drainage pathway. Even if your tear glands are not producing more tears than usual, the tears have nowhere to go, so they spill over the lower eyelid. In reality, you are usually getting hit with both increased production (from the nasal reflex and systemic inflammation) and decreased drainage (from duct compression) simultaneously, which is why sinusitis can make the eyes stream more than a simple head cold does.
This drainage blockage can also make the eyes feel puffy and heavy, especially in the morning after lying flat all night, when sinus pressure tends to be at its worst. Some people with chronic or recurrent sinusitis develop persistently watery eyes as one of their hallmark symptoms, even between acute flare-ups, because the nasolacrimal duct remains partially obstructed by chronic mucosal thickening.
Allergies Versus Infections
Watery eyes are one of those symptoms that sit at the crossroads of infection and allergy, and people frequently confuse the two. The mechanisms overlap: both allergies and infections inflame the nasal mucosa, both trigger the nasonasal reflex, and both release histamine. But there are practical differences worth knowing.
Allergic tearing tends to come with intense itching. The itch is driven by a specific immune pathway involving IgE antibodies and mast cell degranulation that infections generally do not activate in the same way. If your eyes are watery and itchy but you do not have a fever, body aches, or thick discolored nasal discharge, allergies are the more likely culprit. Infectious tearing tends to be accompanied by other systemic symptoms like fatigue, sore throat, and fever, and the nasal discharge often starts clear but turns thick and yellowish or greenish as the infection progresses.
The distinction matters because the treatments diverge. Allergic eye watering responds well to antihistamine eye drops and avoiding the allergen. Infectious eye watering is best addressed by treating the underlying infection and managing congestion. Using antihistamine eye drops during a viral cold will not hurt you, but they will not address the primary reflex-driven tearing either. Meanwhile, chronic exposure to allergens can lead to hyperresponsiveness of the nasal mucosa, where ion channels upregulate to increase the sensitivity and potency of the reflex response.1PubMed. Nasonasal reflexes, the nasal cycle, and sneeze This means that someone with longstanding allergies may have a hair-trigger nasal reflex that produces exaggerated tearing in response to even a mild cold.
What Your Tears Reveal About Your Health
An area of growing research interest is the idea that tears are not just a byproduct of being sick but may contain molecular fingerprints of what is going on inside the body. Tears are a relatively accessible body fluid compared to blood, and collecting them is far less invasive than drawing a blood sample. Researchers have begun profiling the proteins, lipids, and metabolites in tears to see how disease processes alter their composition.3PubMed Central. Tear fluid biomarkers in ocular and systemic disease: potential use for predictive, preventive and personalised medicine
The practical applications are still early-stage, but the concept is compelling. If certain inflammatory markers in tears rise predictably during specific infections, a simple tear sample could someday help distinguish viral from bacterial illness or flag complications earlier. For now, the takeaway for the general reader is that the extra tears your body produces when you are sick are not just mechanical overflow. They carry immune proteins like lysozyme and lactoferrin that actively fight pathogens on the eye’s surface. The increased tear flow during illness is partly a defense mechanism: it flushes the conjunctival surface, delivers antimicrobial proteins, and washes away viral particles before they can establish a foothold in the ocular tissue.
Practical Ways to Manage the Tearing
Most watery eyes during a cold or flu do not need specific treatment. They resolve on their own as the underlying illness clears. But if the constant tearing is bothersome, especially if it is causing skin irritation around the eyes or making it hard to see clearly, a few approaches help.
- Treat the congestion: Because the nasal reflex is the primary driver, anything that reduces nasal swelling will often reduce tearing. Saline nasal rinses, nasal decongestant sprays (limited to a few days to avoid rebound congestion), and steam inhalation can all help open the nasal passages and calm the reflex.
- Warm compresses: Placing a warm compress over the eyes for several minutes helps in two ways. It soothes the irritated skin around the eyes, and research on heated eye masks shows they raise eyelid temperature and improve the stability and thickness of the tear film’s lipid layer, which reduces the watery overflow that happens when the tear film is unstable.4PubMed Central. Effect of a commercially available warm compress on eyelid temperature and tear film in healthy eyes The improvements persisted for at least ten minutes after removing the compress in the study, so even brief sessions help.
- Stay hydrated: This sounds generic, but dehydration during illness concentrates the tear film and can paradoxically increase reflex tearing as the glands try to compensate for a poor-quality tear layer. Keeping up fluid intake supports a more balanced tear film.
- Gentle blotting: Wiping tears aggressively with tissues irritates the delicate periorbital skin and can introduce bacteria. Blotting gently with a clean, soft cloth is better for the skin and reduces the risk of secondary eye infection.
Over-the-counter artificial tears can also provide comfort, particularly if the illness has disrupted the normal tear film and your eyes feel alternately watery and dry. This sounds contradictory, but it is common: a disrupted tear film evaporates too quickly, triggering a compensatory flood of watery reflex tears that lack the normal lipid and mucin layers. Artificial tears supplement the stable tear film and can break that cycle.
When to See a Doctor About Eye Symptoms During Illness
Simple watery eyes during a cold are almost never a reason to seek medical care on their own. But certain combinations of symptoms suggest something beyond the normal reflex tearing and warrant a closer look.
If your eyes become significantly red, produce thick yellow or green discharge, or feel painful rather than just watery, you may have developed viral or bacterial conjunctivitis. Bacterial conjunctivitis can require antibiotic eye drops. If you develop sensitivity to light, blurred vision that does not clear with blinking, or severe pain in or around the eye during a sinus infection, this can indicate that the infection is affecting deeper structures near the orbit, a situation that needs prompt evaluation. Periorbital or orbital cellulitis, while uncommon, is a known complication of sinusitis and is a medical emergency.
Children deserve extra attention because their sinuses and nasolacrimal ducts are smaller and more easily obstructed, and because they are less able to articulate that their vision is changing or their eyes hurt. Persistent tearing in one eye only, especially with swelling or redness of the eyelid, should be evaluated even during what seems like an ordinary cold. In adults, tearing that persists well after the other cold symptoms have resolved may point to a nasolacrimal duct that was damaged or scarred by the infection, a condition an ophthalmologist can assess and treat.
Why Crying When Sick Feels Different
People sometimes notice that emotional crying feels different when they are already sick, and this is not imagination. Under normal conditions, emotional tears are triggered by a completely separate neural pathway from reflex tears. Emotional crying involves signals from the limbic system (the brain’s emotional circuitry) rather than from irritated nasal nerves. But during illness, the two systems compound each other. Your baseline tear production is already elevated from the nasal reflex and systemic inflammation, so when emotional crying adds its own signal on top, the total output is higher than usual. The tears overflow more quickly, the nose runs more dramatically (because those tears are draining through the already-swollen nasolacrimal duct), and the whole experience feels more intense and harder to control.
There is also a behavioral component. Illness lowers the threshold for emotional distress in most people. Fatigue, discomfort, and feeling generally miserable make it easier to tip into crying, and the resulting tears feed back into the congestion and nasal irritation, which feeds back into more reflex tearing. This loop is why a good cry when you are sick can leave you feeling dramatically more congested and watery-eyed than the same cry would on a healthy day.