The Mysterious Code Cats Use to Communicate

What is a Cat Scratch?

A cat scratch is an injury caused by the claws or teeth of a cat puncturing or tearing the skin. Cat scratches can range from minor surface abrasions to deeper wounds. They often occur when playing rough with a cat, by accident when a cat is frightened, or when trying to handle an aggressive cat (CDC).

Cat scratches can become infected by bacteria from the cat’s mouth called Bartonella henselae that is introduced into the wound. This causes a condition known as cat scratch disease (CSD), which is the most common complication. Symptoms of an infected cat scratch include redness, swelling, pain, pus, and swollen lymph nodes near the scratch (Wikipedia).

While most cat scratches are minor, any break in the skin caused by a cat has the potential to cause infection if the wound is deep and bacteria enters the body. Cat scratches should be cleaned and monitored carefully for signs of infection.

Causes of Cat Scratches

There are several common causes of cat scratches, many related to normal cat behavior:

Playing: Cats frequently play with toys, feet, or hands using their teeth and claws. Even during gentle play, cats may accidentally scratch due to sharp claws.

Petting: Some cats dislike being petted in certain areas like the belly or tail. Scratches can occur if the cat gets overstimulated during petting.

Startling: Surprising a sleeping cat or a cat focused intently on something else can cause them to lash out instinctively.

Redirected aggression: A frightened, frustrated, or excited cat may redirect their energy toward the nearest person if the source of their mood is out of reach.

In addition, scratches commonly occur if people attempt to break up cat fights. Most cat scratches are accidental results of normal cat behavior. However, any cat bite or scratch can potentially cause infections.

Signs of Infection

Some common signs of a cat scratch infection include:

Redness: The area around the scratch or bite often becomes red and inflamed as an infection develops. This happens as your body’s immune system tries to fight off the bacteria.

Swelling: Swelling around the wound is another sign of infection, and is caused by inflammation and fluid buildup in the tissues.

Pus: Pus is made up of dead skin cells, bacteria, and white blood cells. Its presence indicates an active infection. Pus may ooze from the wound site.

Fever: A fever is a key sign your body is fighting an infection. Fevers from cat scratches are often low-grade fevers around 100°F (37.8°C).

Other symptoms like fatigue, poor appetite, and headache can also occur with an infected cat scratch. See a doctor if any of these concerning signs develop after a cat injury. Catching an infection early is important for proper treatment (CDC).

Risk Factors

Certain groups of people are at higher risk of developing complications from cat scratches. According to the CDC, those with weakened immune systems are more likely to develop serious symptoms. This includes people with HIV/AIDS, those taking immunosuppressant medications, and people who have had an organ transplant. Young children under the age of 5 are also at increased risk, as their immune systems are still developing. The elderly may also face greater complications. One study found the average age of patients hospitalized for cat scratch disease was 54 years old.


While most cases of cat scratch disease are mild, some people can experience serious complications. Two of the most common complications are cellulitis and abscess formation at the initial wound site (CDC, 2022). Cellulitis causes the skin to become red, painful, and swollen. Abscesses are pockets of pus that form under the skin. Both cellulitis and abscesses require antibiotic treatment, with abscesses sometimes needing drainage as well.

More severe complications, though rare, can be life-threatening. These include septicemia, a serious bloodstream infection, and disseminated bartonellosis, which occurs when the bacteria spread throughout the body affecting the brain, eyes, heart, or other organs (Cleveland Clinic, 2022). Symptoms vary based on which organs are impacted but can include encephalitis, endocarditis, hepatitis, and osteomyelitis. Disseminated infections often require hospitalization and intravenous antibiotics.

Overall, complications from cat scratch disease are uncommon. But people with weakened immune systems due to conditions like HIV/AIDS, organ transplantation, or cancer treatment are at higher risk (Mount Sinai, 2022). Seeking prompt treatment helps prevent the initial infection from progressing into more dangerous forms.

When to See a Doctor

Most minor cat scratches can be treated at home with basic first aid and do not require medical attention. However, it’s important to monitor the wound for signs of infection and seek medical care if any concerning symptoms develop.

According to Hopkins Medicine, you should see a doctor if the scratch or bite site becomes red, swollen, warm to the touch, or tender [1]. These are signs of a possible bacterial infection that requires evaluation and treatment with antibiotics. Other signs of infection include pus draining from the wound, red streaks extending from the wound, swollen lymph nodes near the scratch, and flu-like symptoms such as fever, headache, fatigue, and joint pain.

You should also seek prompt medical attention if the scratch is on your face or hand, as these areas are at higher risk of infection. Facial wounds in particular can progress quickly. Deep puncture wounds, long scratches, and scratches on people with weakened immune systems also warrant medical care.

Children, pregnant women, seniors, and those with chronic diseases like diabetes or cancer should see a doctor for even minor cat scratches to reduce complications. Starting antibiotics quickly can help prevent serious infection in higher risk individuals.


Cat scratch disease is diagnosed through a combination of a medical history, physical exam, and blood tests. The doctor will take a full history of any recent cat scratches or bites and ask about symptoms like fever, headaches, or joint pain. On physical exam, the doctor will look for signs of infection around the scratch such as redness, swelling, pus, enlarged lymph nodes near the scratch site, or a papule or pustule at the initial wound site. Blood tests can help confirm the diagnosis. These may include:

  • A complete blood count (CBC), which can show increased white blood cells if an infection is present.
  • Testing the blood for antibodies to Bartonella henselae. The presence of these antibodies indicates exposure to the bacteria that causes cat scratch disease.
  • PCR (polymerase chain reaction) – a molecular test that can detect the DNA of the Bartonella bacteria.

Imaging tests like CT scans or MRIs may be done if there are concerns about deeper infection or complications. A lymph node biopsy may also be done to look for the bacteria under the microscope and confirm cat scratch disease. With typical symptoms and exposure history, blood antibody tests are often sufficient to diagnose cat scratch fever without further testing.


If a cat scratch becomes infected, antibiotics may be prescribed to treat the infection. According to the Cleveland Clinic, common antibiotics used include azithromycin, cephalexin, ciprofloxacin, and doxycycline. Draining any abscesses or pockets of pus that form from the infection is also an important part of treatment.

In some cases, a tetanus shot may be recommended if the person’s tetanus vaccination is not up to date. Tetanus is a serious bacterial infection that can occur from deep puncture wounds, like cat scratches. According to, a tetanus booster is often given if it has been more than 5 years since the last tetanus vaccine.

Most mild cat scratch infections can be treated at home with good wound care and over-the-counter pain medication. However, seeing a doctor is recommended if symptoms like redness, swelling, pus, fever, or abscesses develop, indicating a deeper infection requiring prescription antibiotic treatment and/or drainage procedures.

Home Care

Home care after a cat scratch often involves properly cleaning the wound, applying antibiotic ointment, and using warm compresses. It’s important to gently wash cat scratches with soap and warm water to remove debris and prevent infection. Avoid scrubbing the wound, which can cause further damage. After cleaning, apply an antibiotic ointment like Neosporin to help prevent bacterial infection. Keep the wound moist by covering it with a bandage or gauze. If swelling, redness, or inflammation occurs, use a warm, moist compress over the area for 10-15 minutes several times a day. This can help reduce pain and irritation. Monitor the scratch closely over the next several days for signs of infection like pus, red streaks, increased pain or swelling. Seek medical attention if these develop. With proper home care most minor cat scratches can heal within a week. Stay alert for complications and don’t hesitate to contact your doctor if concerns arise.


There are several ways to help prevent cat scratches from happening in the first place:

  • Trim your cat’s nails regularly to keep them blunt and less likely to cause deep scratches. Use cat-safe nail clippers and take care not to cut too close to the quick.
  • Play gently with your cat using toys, not hands or feet, so they don’t learn bad habits. Redirect scratching to appropriate surfaces.
  • Avoid startling your cat suddenly, which may cause them to scratch defensively. Move slowly around them.
  • Reduce stress for your cat by providing a calming environment with places to perch up high, cat furniture, and toys. A stressed cat may be more likely to scratch.

With some simple precautions, you can help minimize scratches. But completely preventing cat scratches may not be realistic for an active, healthy cat. Just be prepared to treat them properly if they do occur.

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