Allergic Conjunctivitis


When people suffer what we commonly call “hay fever,” our noses itch and run, we sneeze and sniffle, and our eyes get red, teary, swollen and itchy. These symptoms are all the result of an allergic response to something in our environment. What you might not know is that the eye itself can become inflamed and sensitive due to allergens, a condition referred to as allergic conjunctivitis.

In any kind of conjunctivitis, the delicate pink tissue just under the eyelids (known as the conjunctiva, plural conjunctivae) will become a deeper pink color. It may also become puffy and swollen. In addition, the eyes will produce copious tears and may become itchy and painful. This collection of changes is referred to as conjunctivitis.

While these symptoms may be initiated by viruses or bacteria, an allergic reaction is the most common cause of conjunctivitis among canines. (The most common cause of conjunctivitis among cats is viral.) Dogs will experience many of the same eye-related (ocular) symptoms as humans when they’re exposed to allergens such as dust, grasses, plants, smoke, and pollen.

Symptoms and Identification

Allergic conjunctivitis appears as a deepened pink swelling of the conjunctivae. It may or may not be accompanied by pain (evidenced by squinting) and excessive lacrimation (tears). Discharge from one or both of the eyes can vary from clear and watery to thick and greenish.

Conjunctivitis is usually diagnosed by visual examination of the area, but the following tests may be performed as part of a comprehensive diagnosis:

  •  Visual inspection

  •  Conjunctival smear (with a sterile cotton swab) for cytological evaluation

  •  Skin scraping around the eye to rule out skin parasites, if a contributing factor

  •  Conjunctival culture (obtained with a sterile cotton swab)

  •  Schirmer tear test (to determine the possibility of dry eye)

  •  Response to treatment for possible concurrent skin disease , especially allergic skin disease

  •  Response to treatment for possible concurrent viral or dental disease

  •  Evaluation for possible concurrent nasal disease

Affected Breeds

While all breeds of dogs are susceptible, those who suffer allergic skin disease at higher rates are clearly overrepresented . These include dogs predisposed to allergic otitis externa (link), flea allergies, atopy, and other forms of allergic skin disease.


Allergic conjunctivitis is considered highly treatable, if frustrating to deal with because of their recurrent nature. Luckily, however, treatment of individual episodes is achieved with relative ease via topical medications.

Treatment is aimed at controlling the clinical signs to keep the eye comfortable. This is usually accomplished with daily topical cortisone drops. However, in severe cases drops are used up to 4 times a day. A decreasing frequency of use is recommended, usually as infrequently as is necessary to relieve any discomfort.

Treatment of underlying allergies is also recommended. For example, if other signs of skin allergy are present as evidenced by itchiness, redness or inflammation of the skin or otitis externa (external ear infections), treatment of these underlying conditions (possibly including allergy testing and desensitizing injections) can be effective in many cases.

To reiterate: it’s crucial to understand that treatment of allergic conjunctivitis always involves an individualized approach to treatment to each case.

Veterinary Cost

The cost of allergic conjunctivitis diagnosis and treatment depends to a large extent on the severity of the episode and the frequency of the issue’s recurrence.

For example, if the condition is mild and occurs infrequently independent of any other obvious manifestations of allergic disease, owners may elect to treat each episode symptomatically. As such, the issue may be less expensive since treatment is then relegated to the cost of simple diagnosis and treatment (typically between $100 and $200).

If, however, more comprehensive diagnostic tests and treatment regimens are recommended, the expenses will often rise significantly. This is especially true if in-depth allergy testing and treatment is required, which may include initial costs of up to $1,000 or $2,000 in some cases.


Preventing allergic conjunctivitis is only achievable by preventing any underlying allergic or ocular diseases whenever possible.


Merck Veterinary Manual (Conjunctiva)

Fontenelle J, Powell C, Gionfriddo J, et al. Effect of topical cidofovir on experimentally induced FHV-1 conjunctivitis (abstract). Vet Ophthalmol 2005;8:444.

Galle LE. Antiviral therapy for ocular viral disease. Vet Clin North Am Small Anim Pract 2004;34:639-653.

Kern TJ. Antibacterial agents for ocular therapeutics. Vet Clin North Am Small Anim Pract 2004;34:655-668.