Feline Herpesvirus (FHV-1): Eye Infections, Flare-Ups & Treatment

Last updated: March 26, 2026

If your cat has ever had a weepy, crusty eye that keeps coming back no matter what you do, feline herpesvirus may be the reason. Feline herpesvirus type 1 — also known as FHV-1 or feline viral rhinotracheitis — is one of the most widespread viral infections in the domestic cat population. It is estimated that the vast majority of cats are exposed to the virus before they reach adulthood, and once a cat is infected, the virus stays with them for life. For many cats the infection remains dormant and causes no problems, but for others it becomes a source of painful, recurring eye disease and respiratory illness that requires ongoing veterinary care.

Understanding feline herpesvirus is essential for any cat owner because the virus is so common, the symptoms can mimic other conditions, and the flare-up cycle can be managed effectively once you know what you are dealing with. This comprehensive guide covers everything from the biology of the virus to at-home care strategies that help keep your cat comfortable between episodes.

What Is Feline Herpesvirus (FHV-1)?

Feline herpesvirus type 1 is an alphaherpesvirus that specifically targets cats. It belongs to the same broad family as human cold sores (herpes simplex virus), though it is species-specific — FHV-1 cannot infect humans, and human herpes viruses cannot infect cats. The virus primarily attacks the tissues of the upper respiratory tract and the eyes, with a particular affinity for the conjunctiva (the mucous membrane lining the eyelids) and the cornea (the clear outer surface of the eye).

After initial infection, feline herpesvirus establishes latency in the trigeminal nerve ganglion — a cluster of nerve cells near the base of the skull. The virus inserts its genetic material into these nerve cells and essentially goes into hiding, undetectable by the immune system. It can remain dormant indefinitely, only to reactivate weeks, months, or years later when the cat’s immune system is compromised or weakened by stress. This latency-reactivation cycle is what makes FHV-1 a lifelong condition rather than a one-time illness.

How Cats Contract Feline Herpesvirus

FHV-1 spreads through direct contact with an infected cat’s saliva, nasal secretions, or eye discharge. Transmission occurs most commonly in the following scenarios:

Queen to kitten: Infected mother cats shed the virus during the stress of pregnancy and nursing, exposing their kittens during the first weeks of life. This is the most common route of initial infection and explains why such a high percentage of the cat population carries FHV-1.

Cat-to-cat contact: Cats living in multi-cat environments — shelters, catteries, foster homes, and multi-cat households — are at elevated risk. Mutual grooming, shared food and water bowls, shared litter boxes, and close sleeping arrangements all facilitate viral spread. Sneezing is a particularly efficient method of transmission, as it aerosolizes virus-laden secretions across short distances.

Contaminated objects: The virus can survive on surfaces, bedding, food bowls, and human hands for a limited time — typically up to 18 hours in a moist environment. While less common than direct contact, fomite transmission is possible in shelter and veterinary settings.

Cats who are stressed, unvaccinated, or immunocompromised are at the highest risk of developing severe symptoms upon initial exposure. Kittens under eight weeks of age are especially vulnerable because their immune systems are not yet fully developed. If you are considering adopting a cat, it is worth knowing that many rescue cats carry FHV-1 — this is completely normal and manageable, not a reason to pass on a wonderful companion.

Symptoms of Feline Herpesvirus Eye Infections

The hallmark of feline herpesvirus is ocular disease — eye infections that range from mild conjunctivitis to severe corneal ulceration. Recognizing the symptoms early allows for faster treatment and better outcomes.

Conjunctivitis: This is the most common eye manifestation of FHV-1. The conjunctiva becomes red, swollen, and inflamed. The affected eye or eyes may appear puffy, watery, or produce a thick, yellowish-green discharge. Many cats hold the affected eye partially or fully closed due to pain and light sensitivity. Conjunctivitis caused by feline herpesvirus can affect one eye or both, though unilateral (one-sided) disease is particularly suggestive of a herpesvirus origin.

Corneal ulcers: FHV-1 can directly damage the cornea, creating painful ulcers on the surface of the eye. Dendritic ulcers — branching, tree-like lesions visible under special staining — are considered virtually diagnostic of feline herpesvirus because they are so characteristic of the virus. Deeper ulcers can develop if left untreated, potentially leading to corneal scarring, perforation, or even loss of the eye in severe cases.

Corneal sequestrum: In chronic or recurrent FHV-1 infections, a dark brown or black plaque can develop on the cornea. This dead corneal tissue, called a sequestrum, is painful and usually requires surgical removal. Certain breeds, including Persians and Himalayans, appear predisposed to this complication. You can learn more about breed-specific health tendencies in our cat breeds directory.

Symblepharon: Severe or untreated FHV-1 conjunctivitis — particularly in young kittens — can cause the conjunctiva to adhere to itself or to the cornea, forming permanent adhesions called symblepharon. This can restrict eye movement, impair vision, and cause chronic tearing.

Upper Respiratory Symptoms Beyond the Eyes

While eye disease is the most recognizable feature of feline herpesvirus, the virus also causes upper respiratory illness that can range from a mild cold to severe pneumonia in immunocompromised cats.

Sneezing and nasal discharge: Frequent sneezing, often with clear or mucoid nasal discharge, is one of the earliest and most common signs of an FHV-1 flare-up. The discharge may become thick and purulent if secondary bacterial infection develops. Chronic sneezing can persist in some cats even between active viral episodes due to permanent damage to the nasal turbinates — the delicate structures inside the nose.

Fever and lethargy: During an active primary infection or a significant flare-up, cats may develop a mild to moderate fever (above 39.2 degrees Celsius or 102.5 degrees Fahrenheit) and become noticeably less active. Reduced appetite is common, partly because congestion impairs their sense of smell and partly because they simply feel unwell.

Oral ulcers: FHV-1 can cause painful ulcers on the tongue, gums, and palate. Cats with oral ulcers may drool, refuse food, or paw at their mouths. This symptom is more commonly associated with feline calicivirus, another major upper respiratory pathogen, but feline herpesvirus can cause it as well.

What Triggers Feline Herpesvirus Flare-Ups?

Because feline herpesvirus lives in a dormant state within nerve cells, flare-ups are triggered by anything that weakens or stresses the immune system. Understanding these triggers is the key to reducing the frequency and severity of recurrences.

Stress: This is by far the most common trigger. Moving to a new home, introduction of a new pet, changes in household routine, boarding, veterinary visits, loud construction noise, and even rearranging furniture can be enough to reactivate the virus. Cats are creatures of habit, and disruptions to their environment register as stress even when they seem minor to humans.

Concurrent illness: Any other disease that taxes the immune system — from a urinary tract infection to dental disease to cancer — can allow FHV-1 to reactivate. Cats recovering from surgery or general anesthesia are also at increased risk.

Corticosteroid use: Corticosteroids (such as prednisolone or dexamethasone) suppress the immune system and can trigger severe feline herpesvirus reactivation. This is critically important in veterinary ophthalmology because corticosteroid eye drops are commonly used for other inflammatory eye conditions — but using them in a cat with active or suspected FHV-1 can dramatically worsen corneal ulceration and potentially lead to vision loss.

Seasonal changes and environmental factors: Some owners report that their cat’s flare-ups correlate with seasonal transitions, particularly the colder months. While FHV-1 is not seasonal in the way human cold and flu viruses are, changes in humidity, temperature, and indoor air quality can stress the respiratory system and may contribute to reactivation.

Diagnosis of Feline Herpesvirus

Diagnosing feline herpesvirus often relies on clinical signs and history rather than a single definitive test. Your veterinarian will consider the following factors when evaluating your cat.

Clinical examination: The combination of conjunctivitis, corneal ulcers (especially dendritic ulcers identified with fluorescein staining), nasal discharge, and sneezing in a cat — particularly with a history of recurrence — is highly suggestive of FHV-1. Many veterinarians diagnose and begin treatment based on clinical presentation alone.

PCR testing: Polymerase chain reaction (PCR) testing can detect FHV-1 DNA from conjunctival, corneal, or oropharyngeal swabs. A positive PCR confirms active viral shedding, but a negative result does not rule out latent infection — the virus may simply be hiding in the trigeminal ganglion and not actively present in the sampled tissue at that moment.

Fluorescein staining: This simple, non-invasive test involves applying a fluorescent dye to the surface of the eye. Under a special light, corneal ulcers glow green, revealing their size, depth, and pattern. The branching dendritic pattern is a telltale sign of feline herpesvirus.

Treatment Options for Feline Herpesvirus

There is no cure for feline herpesvirus — once infected, a cat carries the virus permanently. Treatment focuses on controlling active flare-ups, alleviating symptoms, preventing secondary infections, and reducing the frequency of future episodes.

Antiviral medications: Famciclovir is currently the most widely used systemic antiviral for treating FHV-1 in cats. It is given orally (as a tablet or compounded liquid) and works by inhibiting viral replication. Famciclovir has a good safety profile in cats and is the first-line antiviral choice for moderate to severe flare-ups. Topical antiviral eye medications — including idoxuridine, cidofovir, and trifluridine — may be prescribed for corneal ulcers, applied directly to the affected eye several times daily.

Antibiotic eye drops or ointment: While antibiotics do not treat the herpesvirus itself, secondary bacterial infections frequently complicate FHV-1 eye disease. Topical antibiotics such as erythromycin or oxytetracycline are commonly prescribed to prevent or treat these secondary infections and reduce discharge.

Lysine supplementation: L-lysine has been widely recommended for decades as a supplement to reduce FHV-1 flare-ups. The theory is that lysine competes with arginine, an amino acid the virus needs to replicate. However, recent studies have produced mixed results, and some veterinary researchers have concluded that lysine supplementation may not be as beneficial as once believed. Discuss this with your veterinarian — some cats do appear to improve with lysine, but it should not replace proven antiviral therapy.

Supportive care: Keeping the eyes and nose clean, ensuring adequate hydration, maintaining nutrition (warming food to enhance aroma for congested cats), and using a humidifier to ease breathing are all important components of home care during a flare-up. For cats that stop eating due to nasal congestion, appetite stimulants or even temporary feeding tubes may be necessary in severe cases.

Long-Term Management and Prevention

Managing feline herpesvirus is a marathon, not a sprint. The goal is not to eliminate the virus — that is not possible — but to minimize the frequency and severity of flare-ups so your cat can live a comfortable, happy life.

Minimize stress: Create a calm, predictable environment. Maintain consistent routines for feeding, play, and sleep. Provide vertical space (cat trees, shelves), hiding spots, and separate resources (food bowls, water stations, litter boxes) in multi-cat households. If a stressful event is unavoidable — such as a move or a new baby — consider using synthetic feline pheromone diffusers (such as Feliway) to ease the transition. Gradual introductions of new pets, rather than sudden ones, also reduce stress significantly.

Vaccination: The FHV-1 vaccine is part of the core FVRCP vaccination protocol recommended for all cats. While the vaccine does not prevent infection entirely, it significantly reduces the severity of disease in cats exposed to the virus. Kittens should receive their initial vaccination series starting at six to eight weeks of age, with boosters as recommended by their veterinarian. Adult cats benefit from regular booster vaccinations to maintain protective immunity.

Immune system support: A high-quality diet, regular veterinary check-ups, prompt treatment of any concurrent illness, and avoidance of unnecessary corticosteroid use all help keep the immune system strong and the virus in check. Some veterinarians recommend omega-3 fatty acid supplementation or probiotics as additional immune support, though evidence for their specific effect on FHV-1 is limited.

Environmental hygiene: In multi-cat households or foster situations, isolate cats showing active symptoms to prevent spread to other cats. Clean food bowls, water dishes, bedding, and litter boxes regularly. The virus is susceptible to most common household disinfectants, including dilute bleach solutions (1:32 dilution), making environmental decontamination straightforward.

Prognosis and Quality of Life

The vast majority of cats with feline herpesvirus live normal, full-length lives. Most carriers experience only occasional, mild flare-ups that resolve with treatment within one to two weeks. A smaller percentage of cats — particularly those with compromised immune systems or severe initial infections as kittens — may develop chronic eye disease requiring ongoing veterinary management.

Cats with FHV-1 make wonderful companions. The condition is manageable, not a death sentence, and it should never be a reason to avoid adopting a cat who needs a home. Many shelter and rescue cats carry the virus, and with consistent care they thrive in loving households. If you are ready to give a cat a second chance, browse adoptable cats near you and take the first step toward changing a life.

Frequently Asked Questions

Can feline herpesvirus spread to humans or dogs?

No. Feline herpesvirus type 1 is species-specific to cats. It cannot infect humans, dogs, or other animals. Similarly, human herpes simplex virus (which causes cold sores) cannot infect cats. If you have other cats in the household, however, they are at risk of contracting FHV-1 from an infected cat during active shedding periods — especially if they are unvaccinated, very young, or immunocompromised.

How long does a feline herpesvirus flare-up typically last?

Most FHV-1 flare-ups last between seven and fourteen days with appropriate treatment. Mild episodes — limited to some sneezing and minor eye discharge — may resolve on their own within a week. More severe flare-ups involving corneal ulcers or significant respiratory symptoms usually require veterinary treatment and may take two to three weeks to fully resolve. If symptoms persist beyond two weeks despite treatment, follow up with your veterinarian to rule out complications or secondary infections.

Is feline herpesvirus the same as feline calicivirus?

No, though the two are often confused because they both cause upper respiratory infections in cats. Feline herpesvirus (FHV-1) and feline calicivirus (FCV) are different viruses with overlapping but distinct symptom profiles. FHV-1 tends to cause more prominent eye disease and corneal ulcers, while FCV is more commonly associated with oral ulcers, limping syndrome, and sometimes pneumonia. A cat can be infected with both viruses simultaneously. Both are included in the core FVRCP vaccine, and both are common in shelter and multi-cat environments.

Should I adopt a cat that has been diagnosed with feline herpesvirus?

Absolutely. A feline herpesvirus diagnosis is not a reason to avoid adoption. The virus is so common that many cats carry it without their owners ever knowing. With routine veterinary care, stress management, and treatment during flare-ups, most FHV-1-positive cats live healthy, happy lives with minimal impact on their daily routine. Visit our adoption page to find cats waiting for a loving home — many of them would benefit from the stable, low-stress environment of a permanent family.

Can indoor-only cats get feline herpesvirus?

Yes. Most cats contract feline herpesvirus as kittens from their mother before they ever go outdoors. An indoor-only cat that was exposed as a kitten already carries the virus in latent form. Additionally, new cats brought into the household — including foster cats or newly adopted cats — can introduce the virus. Indoor-only cats are still recommended to receive the FVRCP vaccination as part of their core vaccine schedule.

When should I take my cat to the vet for eye symptoms?

Any time your cat shows eye discharge, redness, swelling, squinting, or cloudiness in the eye, a veterinary visit is warranted. Eye conditions can deteriorate rapidly in cats, and what begins as mild conjunctivitis can progress to a deep corneal ulcer within days if left untreated. If your cat is pawing at their eye, keeping it shut, or if you notice any change in the appearance of the cornea (cloudiness, dark spots, or visible irregularities), seek veterinary care promptly. Early treatment is always more effective and less costly than managing advanced disease.