Epistaxis (bleeding from the nose) is more common in dogs than in cats, in my experience, probably because most cats are indoor pets these days. It can occur from one or both nostrils and can vary from slight bleeding that usually stops without treatment to profuse, possibly life threatening bleeding, that resists treatment. As with most abnormal conditions your pet may suffer, proper treatment depends upon establishing the cause.
Some incidents start with sneezing and traces of blood in the discharge from the nose while others can start with alarming, and profuse, bleeding. Any cause of persistent and/or violent sneezing can result in a nosebleed. The most common cause is a foreign body such as a foxtail, grass seed (awns), a small blade of grass or a burr. Other causes of sneezing are nasal infections from bacterial and/or fungal organisms and, of course, allergies that initiate sneezing episodes. In rare cases, the infection from a rotten tooth can extend into a nasal sinus and/or the nasal cavity and cause bleeding. Of course, trauma to the head or nose can result in a bleed and cancers of the nasal cavity, particularly hemangiosarcoma, frequently invade the nasal cavity and result in persistent bleeding.
Less common causes include problems with blood clotting that can result from hemophilia or von Willebrand’s disease (a specific type of hemophilia) and hypertension (high blood pressure). The ingestion of warfarin-based rodent poisons, either directly or after eating a rodent poisoned by one of these agents, can be a cause, as well as systemic infections that involve the blood (septicemia) or bone marrow. The bacteria that responsible for Rocky Mountain Spotted Fever and Ehrlichiosis can cause epistaxis. Other infectious causes include the feline leukemia virus (FeLV) or feline immunodeficiency virus (FIV) in cats. Very ill animals can develop disseminated intravascular coagulation (DIC) with nosebleeds, as can animals with immune-mediated thrombocytopenia. The use of some drugs including methimazole (a drug used to treat animals with a hyperthyroid condition), estrogens, sulfa drugs and some chemotherapeutic treatments for cancer can cause bleeding as well.
If your pet has a nosebleed first try to keep it calm, then hold an ice pack on top of the muzzle. If the bleeding stops then returns, or does not stop, take it to your veterinarian. Do not treat your pet with aspirin or non-steroidal anti-inflammatory agents (NSAIDs). Tell your vet if the animal has been on any kind of medication, been exposed to rat poison or other pesticides, dead rodents, or to a place where s/he could have sniffed up a grass awn or other seed head. You must tell your vet if your pet has been roughhousing with other animals, sustained a trauma to the head or face, been sneezing or rubbing at the nose, had blood in the mouth or gums, a black tarry stool or had “coffee-ground” vomiting. Any of these signs could help with the diagnosis.
After a thorough physical exam, your veterinarian may need to examine the nasal cavities with a small endoscope, do blood work, radiographs, nasal swab cultures and antibiotic sensitivity tests and/or fungal cultures and possibly allergy testing. In cases of neoplasia (cancer), a CT or MRI scan may be necessary. The good news is that most nosebleeds are not serious and once the cause is determined and removed the nosebleed will no longer be a problem.