The Dark Truth Behind Your Cat’s Mysterious Black Sickness


Black discharge coming from a cat’s eyes can be alarming for pet owners. This article will cover the possible causes, diagnosis, and treatments for black eye discharge in cats. The most common reasons a cat may have black discharge include dental disease, upper respiratory infections, other bacterial or viral infections, allergies, and cancer. While black eye discharge can seem serious, it often clears up with proper veterinary treatment. This article provides an overview of why a cat may develop black discharge around their eyes, how it can be diagnosed, and the available treatment options.

Possible Causes

There are a few common causes for black crusty discharge from a cat’s nose:

Dental Disease

Dental disease like gingivitis can cause nasal discharge and black crusts around a cat’s nose. Bacteria from plaque buildup in the mouth can enter the sinuses and lead to infection and inflammation. This causes thick, discolored nasal discharge that dries into black crusts (

Upper Respiratory Infections

Upper respiratory infections from bacteria, viruses, or fungi often cause nasal congestion and discharge. Infected discharge is usually yellow, green, or bloody, but can turn black when it dries and oxidizes on the nose (

Other Infections

Fungal infections, abscesses, and tooth root infections can also lead to black nasal discharge in cats. The infections cause inflammation and infected discharge that crusts into black spots on the nose.

Dental Disease

Dental disease is very common in cats, with over half of cats over 3 years old having some form of it (Source). Dental disease refers to conditions affecting the teeth and gums, such as gingivitis, periodontitis, tooth resorption, and tooth abscesses. These conditions are often very painful for cats but symptoms can go unnoticed by owners.

One symptom of advanced dental disease is a black discharge from the mouth or nose. This occurs when infection from severe gum inflammation, tooth abscesses, or exposed tooth pulp enters the sinuses or upper respiratory tract (Source). The discharge is usually thick, black or brown, and foul smelling.

Other symptoms of dental disease that may lead to black discharge include difficulty eating, weight loss, bad breath, loose or broken teeth, bleeding from the mouth, drooling, facial swelling, and nasal discharge. Cats also often stop grooming when their mouths are painful. Early diagnosis and treatment is important to stop infection from worsening and spreading.

Upper Respiratory Infections

Upper respiratory infections (URIs) are common in cats and are caused by both viruses and bacteria. The most common viruses that lead to URIs in cats include feline herpesvirus-1, feline calicivirus, and feline coronavirus. These viruses can cause inflammation of the nasal passages, sinuses, throat, windpipe, and sometimes the eyes.

Bacterial infections often occur secondary to these viral infections. The most common bacteria involved are Bordetella bronchiseptica, Chlamydophila felis, and Mycoplasma felis. These bacteria can lead to more severe respiratory illness on top of the viral infection.

Symptoms of upper respiratory infections include nasal discharge, sneezing, coughing, eye discharge, reduced appetite, and lethargy. The discharge is often thick and can be clear, yellow, green, or reddish-brown tinged with blood. Ulcers may also form in the mouth. Some cats can develop chronic URIs that persist long-term. Without treatment, URIs can lead to pneumonia or other serious complications (Source).

Other Infections

Less common infections that could potentially cause black discharge in cats include:

Fungal infections – Fungal infections on the skin, ears, or other body parts can cause black greasy discharge. Symptoms may include hair loss, redness, thickened skin, and a bad odor. Fungal infections can be treated with medicated shampoos, oral medications, or topical creams prescribed by a veterinarian. In severe cases, surgery may be required.12

Abscesses – Abscesses are pockets of pus under the skin often caused by bacterial infections. They can rupture and leak a black, bloody, or yellow discharge. Abscesses require drainage, flushing, and antibiotics from a vet.

Plague – Although rare, cats can get plague from infected rodents or fleas. The bacterial infection causes swollen lymph nodes that can rupture and ooze black material. Plague is life-threatening if left untreated.3

Overall, any unusual discharge in cats should be evaluated by a veterinarian to diagnose and treat the underlying condition.


Allergies are a common cause of black nasal discharge in cats. Just like in humans, allergies in cats can cause inflammation and increased mucus production in the nasal passages and sinuses. This excess mucus can dry out and cause the formation of black crusty discharge around the nose and eyes.

Cats can be allergic to things like pollen, dust mites, molds, and even ingredients in their food. Inhalant allergies like pollen and dust cause immune reactions when breathed in. This leads to itching, sneezing, and nasal discharge. Food allergies generally cause skin reactions like itching and hair loss in addition to respiratory signs.

Allergic rhinitis is the medical term for inflammation of the nasal passages caused by an allergic reaction. Chronic rhinitis leads to ongoing nasal discharge, which dries into a black crust on the nose and face. Allergies should be suspected especially if the cat has recurrent bouts of sneezing and nasal discharge 1.

Diagnosing allergies usually involves testing for allergic reactions, changing diets, and ruling out infections. Treating allergies involves avoiding triggers, medications, and immunotherapy. Keeping the cat’s face clean can help remove dried discharge. Overall management of allergies is needed to stop ongoing inflammation and black nasal crusting.


Nasal cancer, though rare in cats, can also lead to black nasal discharge. Feline nasal cancer, also known as nasal adenocarcinoma, accounts for around 1-2% of all feline tumors. Some main symptoms of nasal cancer include nasal discharge containing blood, mucus, or pus; noisy breathing sounds; facial deformity or swelling; and ocular discharge or bulging eyes.

The exact cause of nasal cancer in cats is unknown, but long-nosed breeds like Siamese are more predisposed. The cancer usually starts inside the nose and invades outward into the sinus cavities and face over time. As the tumor grows, it can obstruct nasal passages and lead to the accumulation of bloody, black discharge.

To diagnose nasal cancer, vets will perform advanced imaging like CT scans or rhinoscopy to view inside the nasal passages and take biopsies. Treatment usually involves some combination of surgery, radiation therapy, and chemotherapy. Though nasal cancer often carries a poor prognosis, early diagnosis and treatment can prolong a cat’s survival and comfort.


Veterinarians will perform a full physical exam on the cat, checking the ears, eyes, nose, and mouth for signs of infection or other issues. They will take the cat’s temperature and feel its lymph nodes for enlargement, which can indicate infection. The vet will also listen to the cat’s breathing with a stethoscope.

To identify the specific cause of the nasal discharge, the vet may collect samples for further analysis. They may take a swab of the nasal discharge or do a nasal flush to collect discharge deep in the nasal passages. These samples can be cultured to identify a bacterial or fungal infection. Cells from the discharge may also be examined under a microscope for signs of cancer or other abnormalities.

Imaging tests like x-rays or CT scans of the nose and sinuses may be recommended. These can reveal nasal polyps, tumors, tooth root abscesses, foreign objects lodged in the nasal passages, or other issues causing discharge. Rhinoscopy, where an endoscope is inserted in the nose for visual examination, may also be performed.

Blood work may be done to look for infections or other systemic illnesses. Allergy testing can also help determine if allergies are the root cause of chronic nasal inflammation and discharge.

Through a combination of a thorough physical exam, sample analysis, and imaging, the veterinarian will seek to pinpoint the reason for the cat’s nasal discharge and recommend appropriate treatment.


Treatment for a cat with a black, crusty nose will depend on the underlying cause. Here are some common treatment options:

If there is a bacterial or viral infection, the vet may prescribe antibiotics or antivirals. In the case of herpesvirus, the vet may recommend antiviral medication such as famciclovir. Upper respiratory infections are often treated with antibiotics like doxycycline or azithromycin. The cat’s eyes and nose may need to be cleaned regularly to remove discharge.

For allergies, the vet may recommend medication like antihistamines or corticosteroids to reduce inflammation and itchiness. Omega-3 fatty acids may also help soothe allergic reactions. Removing potential allergens from the home environment can help as well.

If a tumor or cancerous growth is the cause, treatments may include surgical removal, chemotherapy, or radiation. Biopsies are often needed to confirm cancer and determine the best course of treatment.

In any case, keeping the cat’s face clean and free of discharge will help prevent worsening of the crusty nasal mucus. Gentle cleaning with a warm, damp cloth may be recommended. Topical antibiotic ointment can also help heal any raw skin.

Getting to the root cause with proper veterinary diagnosis is key to finding the most effective treatment. With appropriate treatment guided by a vet, most cats can recover well from nasal discharge and crusty noses.



There are several preventative measures cat owners can take to help minimize the risk of their cat developing black nasal discharge or crusty buildup around the nose and mouth. Regular dental cleanings and care are very important, as dental disease is a common cause of upper respiratory issues that can lead to nasal discharge (cite url 1). Your veterinarian can perform professional dental cleanings and examine your cat’s mouth to look for signs of gum disease or other problems.

At home, you should brush your cat’s teeth daily if possible using a soft toothbrush and cat-safe toothpaste. This helps reduce plaque and tartar buildup. You can also feed dental cat food or treats to help control tartar. Limiting exposure to irritants like dust, smoke, and harsh chemicals can also help reduce nasal irritation and discharge (cite url 2). Keep your home clean and well ventilated and avoid using fragranced cleaning products, air fresheners, or other strong chemicals around your cat.

It’s also important to keep your cat’s vaccines up to date and bring them to the vet for wellness checks twice a year. This allows early detection and treatment of any infections before they become more serious. Feeding a high-quality diet supports good immune health. Reduce stress for your cat as much as possible since stress can negatively impact immune function (cite url 3). Proper preventative care helps keep your cat’s respiratory system healthy and reduces the chances of problematic nasal discharge occurring.

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