Testing for Sneezing and Nasal Discharge

By Courtney Barnes, BSc, DVM; Krista Williams, BSc, DVM, CCRP; Kristiina Ruotsalo, DVM, DVSc, Dip ACVP & Margo S. Tant BSc, DVM, DVSc

What causes sneezing and nasal discharge in a pet?

Sneezing and nasal discharge can appear together or can occur as separate problems. They are associated with disorders of the nasal cavity, nasal sinuses, or both.

While an occasional sneeze is perfectly normal, repeated bouts of vigorous sneezing suggests irritation of the nasal cavity caused by:

  • viruses (especially in cats)
  • air-borne irritants, such as powder, dust, fumes, smoke, or aerosol sprays
  • foreign material, such as plant fragments
  • nasal mites in dogs (rare)
  • conditions that cause nasal discharge

Nasal discharge may be caused by several different conditions such as:

  • infection of the nasal cavity or nasal sinuses by viruses, fungi, or bacteria
  • masses, such as polyps or tumors
  • inflammation caused by foreign material
  • irritation caused by nasal mites (dogs)
  • allergies
  • conditions extending from the mouth such as abscessed tooth roots or tumors
  • disease deep in the airways

How is the cause of sneezing or nasal discharge determined in my pet?

The search for answers starts with a complete history and physical examination. A pet’s history is the information you give your veterinarian about your pet’s illness. In a sneezing pet this would include details about how long the sneezing has been going on, possible contact with other pets, whether there is nasal discharge, and whether the pet is depressed or lethargic. This information can be very helpful in determining the cause of your pet’s signs. For example, a cat that starts to sneeze after being at a boarding kennel may have a viral infection called feline viral rhinotracheitis; a dog that suddenly starts to sneeze violently after coming in from outdoors may have a bit of grass or small seed stuck in the nasal passage.

A thorough physical examination involves looking at all parts of the body, including the ears, nose, mouth, and throat, and listening to the heart and lungs with a stethoscope. This may provide clues about the cause of sneezing or nasal discharge.

"A thorough physical examination involves looking at all parts of the body."

For example, a dog with longstanding nasal discharge and a swelling over the nasal region may have a nasal infection or a nasal tumor; a sneezing cat that also has mouth ulcers likely has a viral infection; a dog with an abscessed tooth may be sneezing because infection has spread from the tooth root into the nasal cavity.

History and physical examination are important, but additional diagnostic tests will likely be needed, and your veterinarian may recommend screening tests. These are simple tests that provide information about the overall health of the pet and may provide further clues about the underlying problem.

What screening tests might be recommended, and what can they tell us?

The basic screening tests include a complete blood count, serum biochemistry profile, and urinalysis. If the nasal discharge is bloody, coagulation testing might also be done to assess the body’s blood clotting system.

Complete blood count (CBC)

The CBC is a simple blood test that provides information about the different cell types in blood, including red blood cells, which carry oxygen to the tissues; white blood cells, which fight infection and respond to inflammation; and platelets, which help the blood to clot.

The CBC provides details about the number, size, and shape of the various cell types and identifies the presence of abnormal cells. See handout “Complete Blood Count” for further information.

In a pet with sneezing and nasal discharge, some changes that could be seen on the CBC include:

  • Anemia (a decrease in the number of red blood cells, packed cell volume, and hemoglobin). This could be a sign of bleeding in the nasal passages. It could also be a sign of longstanding inflammation associated with infection or cancer.
  • High numbers of white blood cells suggest underlying infection or inflammation.
  • Low numbers of white blood cells could be a sign of acute viral or severe bacterial infection.
  • Low platelet count could explain a sudden onset of a bloody nasal discharge.

Serum biochemistry profile

Serum biochemistry profile is the chemical analysis of serum, which is the liquid part of blood that remains after the cells and clotting factors have been removed. There are many substances in serum, including proteins, enzymes, fats, sugars, hormones, and electrolytes. Measuring the levels of these substances provides information about the organs and tissues in the body, as well as the metabolic state of the pet. Changes and abnormalities found in the biochemistry profile can help to diagnose a variety of diseases and disorders. See handout “Serum Biochemistry” for further information.


This is a simple test that analyzes the physical and chemical composition of urine. It measures how well the kidneys are working, identifies inflammation and infection in the urinary system, and helps to detect diabetes and other metabolic disturbances. Urinalysis is important for the proper interpretation of the serum biochemistry profile and should be done at the same time as blood testing. See handout “Urinalysis” for further information.

Serum biochemistry and urinalysis are done to see if the sneezing and nasal discharge are part of a larger systemic illness that is affecting the whole body. The tests also help to ensure it is safe to put a pet under general anesthesia in order to investigate the cause of the sneezing and nasal discharge.

Coagulation testing

Coagulation testing is recommended if the nasal discharge is bloody. The most common screening test is the coagulation profile. In certain breeds of dogs, the von Willebrand’s factor (vWF) test is also recommended. These tests assess the blood clotting system and determine if the bleeding is due to a deficiency in coagulation factors (proteins). They also indicate if a pet might bleed excessively during diagnostic procedures to investigate the cause of the sneezing and nasal discharge.

What specific tests would be recommended to investigate sneezing and nasal discharge?

Nasal swab for cytology. Cytology is the microscopic study of individual cells. This procedure involves collecting a small amount of nasal discharge on a sterile swab and spreading it thinly on a glass slide. This is sent to a referral laboratory for examination by a veterinary pathologist. Cytology can provide information about the health of the cells lining the nasal passage, and can detect inflammatory cells, cancer cells, and infectious organisms such as bacteria and fungi. The swab needs to be quite deep to be diagnostic, however, as superficial cells and bacteria may not be representative of the extent of the problem.

X-rays (radiographs) of the nasal cavity. This usually requires sedation or general anesthetic to help the pet to lie still. Radiographs are useful to detect bone cancer or bone infection, and inflammation or infection in the sinuses.

Nasal flush for cytology. This procedure requires light general anesthesia. A sterile catheter (long tiny tube) is passed up the nose into the nasal cavity. A syringe of sterile fluid is attached to the free end and fluid is flushed into the nasal cavity and quickly suctioned or “re-aspirated” back into the syringe. The re-aspirated fluid contains lining cells, secretions, and other material that has been “washed off” by the flushing action. The collected fluid is sent to a veterinary pathologist for cytological examination. Cytology can identify the types of cells that are present, such as lining cells, inflammatory cells, or cancer cells, and can detect infectious organisms such as bacteria and fungi.

Rhinoscopy. This procedure requires general anesthesia. A small fiberoptic endoscope is passed up the nose into the nasal cavity to look for problems such as inflammation, infection, tumors, ulceration, bleeding, or foreign material such as plant debris. If foreign material is found, it can sometimes be removed using a tiny attachment on the endoscope. The endoscope is also used to collect biopsies from the nasal cavity.

What additional tests may be required?

Additional diagnostic tests are often needed to determine the specific cause of a pet’s sneezing and nasal discharge. Some examples include:

  • Bacterial culture and sensitivity. If bacterial infection is suspected, a sample of the nasal discharge or nasal flush fluid can be sent to a referral laboratory for culture and sensitivity testing. This test helps to determine which type of bacteria is present and which antibiotic is best to treat the infection. Culturing nasal discharge is easiest, but fluid from a nasal flush is the preferred sample for culture since it is less likely to be contaminated by unimportant bacteria from the skin surface.
  • Fungal culture. This is like a bacterial culture, except that it is used to detect fungal infection.
  • Chest X-rays (radiographs) may be recommended if the nasal discharge appears to be related to a problem in the trachea (windpipe) or lungs. Alternatively, if cancer is found in the nasal cavity, then chest X-rays would be recommended to see if the cancer has spread to the lungs.
  • Testing for specific infectious organisms. In addition to bacterial and fungal cultures, a variety of tests can be used to detect infectious organisms. These include the newer DNA-PCR tests and blood tests that detect antibodies in a patient’s blood against specific organisms.
  • Computerized tomography (CT) and magnetic resonance imaging (MRI). These are advanced technologies that are available only at veterinary referral hospitals. CT and MRI scans provide a more detailed image of the skull and nasal sinuses and can often detect small abnormalities that are not evident on X-rays.
  • Biopsy. Cells and tissues are collected from the nasal passages and submitted to the laboratory, where they are examined under the microscope by a veterinary pathologist. Biopsy samples are typically taken during rhinoscopy. It can often provide a definitive diagnosis.

If the cause of a pet's sneezing or nasal discharge cannot be determined by the techniques described above, then surgical exploration of the nasal cavity may need to be performed. This is a difficult procedure and would be done only by a specialized veterinary surgeon.

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