Inflammation in your nasal passages and sinuses during illness triggers a reflex arc that stimulates your tear glands, and that is the main reason your eyes water when you have a cold or the flu. The connection between your nose and your eyes is more direct than most people realize, running through shared nerve pathways that treat nasal irritation and eye lubrication as part of the same job. But the reflex is only part of the story. Your body also ramps up tear production for defensive reasons, and some of the things you do to treat a cold can make the watering worse.
The Nerve Reflex That Links Your Nose to Your Tears
Your nasal passages and your lacrimal glands (the small glands above each eye that produce tears) are wired into the same nerve circuit. The trigeminal nerve, which is the largest nerve in your face, carries sensory signals from both your nasal lining and your eye surface. When your nasal mucosa gets inflamed and swollen during a cold, the nerve endings embedded in that tissue fire off signals. Those signals travel to the brainstem, which sends a return message to your lacrimal glands telling them to start secreting fluid. This happens fast, almost instantaneously, because the pathway evolved to flush irritants out of your eyes before they could do damage.
Research into this reflex has shown that receptors on nerve endings in the nose, when stimulated, initiate a reflex arc that results in immediate tear secretion.1PubMed. Nicotinic acetylcholine receptor stimulation: A new approach for stimulating tear secretion in dry eye disease Under normal circumstances, this pathway exists to respond to things like dust, smoke, or chemical fumes entering your nose. When you are sick, the swelling and mucus production in your nasal passages essentially trick this system into staying active. The inflammation itself acts as a persistent irritant, keeping the trigeminal nerve firing and your tear glands working overtime.
This is also why blowing your nose hard or sneezing tends to make your eyes water even more. Both actions stimulate the nasal lining intensely, sending a burst of sensory input through the same reflex arc. The tearing you get after a big sneeze and the low-grade watering that persists all day during a cold are the same mechanism operating at different intensities.
How the Autonomic Nervous System Keeps the Faucet Running
The reflex from the nose is the trigger, but the actual machinery that keeps tears flowing involves your autonomic nervous system, specifically the parasympathetic branch. When sensory nerves in your cornea, conjunctiva, or nasal mucosa detect irritation, they activate parasympathetic and sympathetic nerves that directly innervate the lacrimal gland. Those nerves release neurotransmitters that cause the gland to secrete water, electrolytes, and proteins onto the eye surface.2PubMed Central. Neural regulation of lacrimal gland secretory processes: relevance in dry eye diseases
When you are healthy, this system operates quietly in the background, keeping your eyes moist with a thin, stable tear film. You produce what are called basal tears at a slow, steady rate throughout the day. You barely notice them. But illness shifts the system into a more aggressive mode. The parasympathetic nerves stay activated because the nasal irritation does not go away, and the result is reflex tearing, the same kind of tear production you get when you chop an onion or step into a cold wind. The difference is that with a cold, the stimulus lasts for days.
Fever adds another layer. When your body temperature rises, your autonomic nervous system is already working harder than usual, regulating blood vessel dilation, sweat production, and other responses. This heightened autonomic activity can spill over into tear production, which is why you may notice your eyes watering more during fever spikes than at other points during your illness.
Tears Are Part of Your Immune Defense
Your body is not just producing extra tears as an accident of crossed wires. Tears contain a surprisingly rich cocktail of antimicrobial compounds that form part of the innate defense system of the eye. The tear film includes classic antimicrobial agents like lysozyme, an enzyme that can break down bacterial cell walls, along with more recently identified compounds such as cationic antimicrobial peptides and surfactant protein-D.3PubMed Central. Antimicrobial compounds in tears Like all mucosal fluids, tears contain a wide range of molecules with known antimicrobial effects.
From an evolutionary perspective, tears have always had functions beyond emotional signaling. Basal tears lubricate and nourish the cornea while keeping it free of dust and bacteria. Reflex tears protect the eye against physical and chemical damage.4ScienceDirect. Emotional tears: What they are and how they work When you are fighting off an infection, increasing the flow of this antimicrobial fluid over the eye surface is a genuinely useful response. Your eyes are a mucosal membrane exposed to the outside world, and pathogens can enter or infect through them. Ramping up tear production during illness washes potential invaders away and coats the eye surface with a fresh layer of protective compounds.
So while the tearing feels like a nuisance, it is actually your body doing something constructive. The reflex was not designed for colds specifically, but the immune benefits of increased tear flow happen to align nicely with the moment you need them most.
When Viruses Target the Eyes Directly
Most of the time, watery eyes during a cold or flu are a secondary effect of nasal inflammation. But some viruses can infect the eyes directly, causing a more intense and distinct kind of tearing. Influenza A viruses, including both avian and human strains, have demonstrated the ability to use the eye as a portal of entry and to cause ocular disease in humans. Among influenza subtypes, H7 viruses stand out for possessing an ocular tropism, meaning they have a particular affinity for eye tissue.5PubMed Central. The eyes have it: influenza virus infection beyond the respiratory tract
Adenoviruses, which cause many common colds, are also well-known for producing conjunctivitis, the red, watery, irritated eyes that people sometimes call “pink eye.” When a virus directly infects the conjunctival tissue, the resulting inflammation stimulates tear production locally rather than through the nasal reflex. This type of tearing tends to be more severe and often comes with visible redness, a gritty sensation, or discharge that is different from the clear, watery overflow you get with plain nasal congestion.
If your eyes are not just watery but also noticeably red, crusty in the morning, or painful, the virus may be affecting your eye tissue directly rather than just triggering a nasal reflex. Viral conjunctivitis usually resolves on its own within a week or two, but it is highly contagious, so washing your hands frequently and avoiding touching your eyes matters more during this kind of illness.
Sinus Congestion and the Drainage Problem
There is also a plumbing explanation. Under normal conditions, your tears drain from the eye surface through small openings in the inner corners of your eyelids, down through the nasolacrimal duct, and into your nasal cavity. This is why your nose runs a little when you cry: the tears are literally draining into your nose. When you have a cold or sinus infection, the nasal tissue swells so much that this drainage pathway can become partially or fully blocked.
When the drain is blocked, tears that would normally flow away quietly instead pool on the eye surface and spill over your lower lid. You are not necessarily producing more tears in this scenario; the tears just have nowhere to go. This is a common contributor to the constant watery-eye feeling during heavy congestion, and it explains why the tearing often gets worse when you lie down, since gravity is no longer helping move fluid through an already narrowed duct.
The result is that you have two forces working at the same time: increased tear production from the nasal reflex and decreased tear drainage from swollen nasal passages. Together, they produce the overflowing, constantly-dabbing-your-eyes effect that makes a bad cold feel even more miserable.
Dehydration, Fever, and Irritated Eyes
It might seem contradictory that your eyes water more when you are sick even though illness often leaves you dehydrated. Fever, sweating, and reduced fluid intake all pull water out of your body, and dehydration changes the composition of your tears. Research has found that tear fluid osmolarity, essentially how concentrated the salts and proteins in your tears are, can serve as a marker of overall hydration status, and dehydration has been associated with development of dry eye syndrome.6PubMed Central. Hydration, fluid regulation and the eye: in health and disease
This creates a somewhat paradoxical situation. When you are running a fever and not drinking enough, your basal tear film can become unstable and overly concentrated, which irritates the eye surface. That irritation triggers compensatory reflex tearing, so your eyes water even though the underlying problem is actually too little moisture. You may notice this as alternating between moments of stinging dryness and sudden watering, a cycle that is common during febrile illnesses and resolves once you rehydrate.
Staying well-hydrated during illness helps not just for the obvious reasons like replacing fluids lost to fever but also because it stabilizes your tear film and reduces the reflex tearing driven by surface irritation. If you find that your eyes feel gritty and then suddenly flood, drinking more fluids is likely to help more than eye drops.
Yawning, Fatigue, and Those Extra Tears
When you are sick, you yawn more, and yawning itself can trigger tearing. The connection is partly mechanical: a big yawn compresses the lacrimal glands and squeezes out tear fluid. But there may also be an autonomic component, since yawning involves a burst of parasympathetic activity that could stimulate tear secretion through the same pathways that nasal irritation uses.
People who are ill tend to yawn more frequently because of fatigue, disrupted sleep, and possibly thermoregulatory mechanisms. Research on chronic yawning has linked the behavior to thermoregulatory dysfunction, with some individuals experiencing significant drops in body temperature following yawning bouts.7SpringerLink. Excessive yawning and thermoregulation: two case histories of chronic, debilitating bouts of yawning When you are feverish, your body may use yawning as one of its tools for cooling, and the tearing that comes with it is a side effect.
This means that even during periods when your nasal congestion is mild, you might still have watery eyes simply because you are exhausted and yawning constantly. It is one of those illness symptoms that compounds with everything else: congestion makes you breathe through your mouth, mouth-breathing dries your throat and disrupts sleep, poor sleep makes you more fatigued, and fatigue makes you yawn more, which makes your eyes water.
Can Cold Medicine Make the Watering Worse?
Some over-the-counter medications you reach for during a cold can actually affect your eyes in unexpected ways. Oral decongestants like pseudoephedrine work by constricting blood vessels throughout the body, including in the delicate tissues around the eye. While they reduce nasal swelling, they can also reduce blood flow to the lacrimal gland and alter the tear film. Animal research on nasal decongestants has found that prolonged use was associated with various ocular tissue changes, including epithelial defects and signs of dry eye.8PubMed Central. Ophthalmic adverse effects of nasal decongestants on an experimental rat model
Antihistamines, another common cold remedy, are even more directly linked to eye dryness. They block histamine receptors throughout the body, including in the lacrimal gland, which reduces tear production. This can lead to the same dry-eye-followed-by-reflex-tearing cycle described earlier. You take an antihistamine to stop your runny nose, it dries out your eyes as a side effect, and then your eyes water more as a compensatory response. The net result can feel like the medicine is not working at all for your eye symptoms, even though it is doing exactly what it is designed to do to your nasal passages.
If watery or irritated eyes are a prominent symptom during your illness, it is worth thinking about whether your medication might be contributing. Using a humidifier, applying preservative-free artificial tears, and staying hydrated can all help counteract the drying effects of these medications without requiring you to stop taking them.
Why Some Illnesses Cause More Tearing Than Others
Not every sickness produces the same degree of watery eyes. Understanding the symptoms of the common cold and influenza involves looking at the specific inflammatory mechanisms driving each symptom, and those mechanisms vary by pathogen.9PubMed Central. Understanding the symptoms of the common cold and influenza Rhinoviruses, which cause most common colds, tend to produce heavy nasal inflammation with lots of mucus but relatively mild systemic symptoms. That heavy nasal involvement means intense stimulation of the nasal-lacrimal reflex, so colds often come with pronounced eye watering.
Influenza, by contrast, tends to produce stronger systemic symptoms like high fever, body aches, and fatigue, with comparatively less nasal congestion early on. You might feel terrible with the flu but have less eye watering than with a mild cold, at least in the first few days. As the flu progresses and nasal symptoms develop, the tearing usually follows. COVID-19 has added another variable, as some patients report conjunctival irritation and tearing as an early or prominent symptom, likely related to the virus’s ability to infect cells through ACE2 receptors present in eye tissue.
Sinus infections (sinusitis) tend to produce the most dramatic tearing, partly because the swelling is more severe and more directly blocks tear drainage, and partly because the inflammation can extend to the tissues surrounding the eye socket. If your eyes water significantly more on one side, that can sometimes indicate that the sinuses on that side are more congested or infected than the other, since the nasal-lacrimal drainage and reflex pathways operate somewhat independently for each eye.
When Watery Eyes During Illness Deserve Medical Attention
For most colds and flu, watery eyes are annoying but harmless and resolve when the illness does. There are a few situations, though, where tearing during illness signals something that needs a closer look.
- Thick or colored discharge: Clear, watery tears during a cold are normal. Thick yellow or green discharge from the eyes, especially with crusting, suggests bacterial conjunctivitis or a secondary infection that may benefit from treatment.
- Pain or light sensitivity: If your eyes do not just water but actively hurt, or if light becomes painful to look at, the inflammation may have spread deeper into the eye. This warrants a visit to a doctor.
- Persistent tearing after illness resolves: If your cold is gone but your eyes keep watering for weeks afterward, the nasolacrimal duct may have been scarred or narrowed by the infection. This is uncommon but can happen after severe sinus infections.
- Vision changes: Any blurriness, floaters, or vision loss during an illness is not a normal tearing symptom and should be evaluated promptly.
For garden-variety cold-related tearing, cool compresses over the eyes, gentle nose-blowing rather than forceful blasts, and adequate hydration do the most to keep you comfortable. The tearing feels excessive because multiple mechanisms are stacking on top of each other simultaneously, but each one is either protective or mechanical, and all of them wind down as the underlying infection clears.