Introduction
A cat scratch is simply when a cat’s claws puncture or scrape a person’s skin, often unintentionally while playing. While most cat scratches are harmless, in some cases they can lead to complications.
The prevalence of cat scratches is not well documented, but they are extremely common, with an estimated 55% occurring in children under 18.
Potential side effects from cat scratches include bacterial infections, cat scratch fever/disease, inflammation, scarring, allergic reactions, rabies, and psychological effects.
Bacterial Infections
Cat scratches can cause bacterial infections, the most common being cat scratch disease (CSD). CSD is caused by a bacterium called Bartonella henselae that is carried in cat saliva. The CDC notes that this bacteria spreads when an infected cat licks a person’s open wound or bites/scratches them, allowing the bacteria to enter the skin.
According to the Johns Hopkins Medicine, symptoms of CSD include fever, headache, poor appetite, exhaustion, and swollen lymph nodes near the scratch or bite. In rare cases it can cause damage to the liver, spleen, eyes, or central nervous system if untreated. CSD is generally treated with antibiotics. Cleaning the wound thoroughly after a cat scratch can help prevent infection.
Other bacteria that can be transmitted by cat scratches or bites include Pasteurella, Streptococcus, Staphylococcus, and Capnocytophaga. These may cause skin infections, abscesses, joint infections, or blood poisoning if they spread. Seeking prompt medical treatment is important for any cat scratch that becomes red, swollen, warm, or tender.
Cat Scratch Fever
Cat Scratch Fever, also known as cat scratch disease (CSD), is caused by a bacteria called Bartonella henselae. This bacteria is carried in cat saliva and can be transmitted through scratches, bites, or even just by a cat licking an open wound. According to research, the annual incidence of CSD is approximately 4.5 cases per 100,000 population in the United States, with children under the age of 18 making up 55% of cases [1].
The most common symptoms of cat scratch fever include fever, fatigue, headache, poor appetite, and swollen lymph nodes near the scratch or bite. The swollen lymph nodes usually occur 3-10 days after the injury and can persist for several weeks to months. Most cases of cat scratch fever resolve on their own without treatment, however antibiotics like azithromycin are sometimes prescribed for more severe cases. Serious complications like encephalitis are rare but can occur in immunocompromised individuals [2].
To help prevent cat scratch fever, it’s important to properly clean any scratches or bites from a cat, avoid rough play, and trim cats’ nails regularly. Children should be supervised when interacting with cats. Promptly treating any scratches or bites can help reduce risk of infection.
Inflammation and Infection
One of the most common side effects of a cat scratch is localized inflammation and infection at the scratch site. According to the CDC, Cat Scratch Disease | Healthy Pets, Healthy People, a person who is scratched by a cat may develop redness, swelling, and pain around the scratch. The scratched area can become infected with bacteria from the cat’s mouth that enter through the broken skin. This causes an inflammatory response as the body tries to fight off the infection.
Cat scratches, even superficial ones, should be cleaned and monitored for signs of infection like increasing pain, redness, warmth, and pus. Seek medical attention if the scratch site shows signs of worsening infection. Treatment may require antibiotics and draining any abscess that forms. Prompt treatment can prevent the infection from spreading into deeper tissues or the bloodstream, which would be a more serious complication.
Fortunately, most minor cat scratches heal without issue if cleaned properly. However, it’s important to watch for localized inflammation and infection and get medical care if the scratch worsens.
Scarring
Cat scratches can potentially cause scarring due to the depth of the wound and healing process. When a cat’s claws scratch the skin, they create a deeper wound than a scrape or surface scratch. This increases the risk of scarring as the wound heals from the deeper layers of skin outward (source).
There are a few ways to minimize scarring from cat scratches (source):
- Clean the wound – Gently wash scratches with soap and water to remove debris and prevent infection. This helps the wound heal cleanly.
- Apply antibiotic ointment – Applying antibacterial ointment can prevent infection which reduces inflammation and scarring.
- Keep moisturized – Keeping the wound moisturized with products like petroleum jelly or aloe can improve healing and reduce scarring.
- Massage – Gently massaging the scar once healed can help break up scar tissue and minimize visible scarring.
- Silicone sheets/gel – Applying silicone sheets or gel to healed scars may improve their appearance.
- See a dermatologist – For severe scars, professional scar revision treatments like laser therapy or dermabrasion can reduce scarring.
While scarring is possible with cat scratches, taking proper care of the wound right away and using scar minimizing techniques once healed can help reduce permanent marks (source).
Allergic Reactions
Some people may experience an allergic reaction to substances found in cat saliva that are introduced through a scratch or bite. According to the Cleveland Clinic, the most common symptoms of an allergic reaction to a cat scratch include:
- Red, raised itchy rash or hives at the scratch site
- Swelling around the scratch
- Itching
- Sneezing, runny nose
- Watery eyes
- Wheezing or difficulty breathing in severe cases
These allergy symptoms typically start within an hour after the scratch and last up to 24 hours. Some people may only experience a localized reaction at the scratch site, while others can have a systemic reaction affecting the whole body.
The best way to prevent an allergic reaction is to avoid direct contact with cats if you know you are allergic. Covering skin when handling cats and washing hands after contact can also help prevent reactions. If scratched, immediately washing the area with soap and water can minimize exposure to allergens.
Rabies
Rabies is an extremely rare but very serious consequence of a cat scratch. Rabies is caused by a virus that attacks the central nervous system and is transmitted through the saliva of infected animals. Cat scratches rarely transmit rabies because the virus is typically spread through bites that break the skin rather than surface scratches (source).
However, if a cat is infected with rabies, its scratches pose a potential risk. According to the CDC, less than 1% of U.S. rabies cases are from cats. Bats are the most common source. The vast majority of documented rabies transmissions to humans are through bites rather than scratches (source).
Initial rabies symptoms are flu-like including fever, headache, and fatigue. As the virus progresses, more serious neurological symptoms emerge including anxiety, confusion, hallucinations, and hydrophobia (fear of water). Rabies is fatal once symptoms appear. However, the disease is preventable if treatment is administered shortly after exposure and before symptoms start (source).
If a cat scratch breaks the skin, immediately wash the wound with soap and water. Contact your doctor to assess your rabies risk and determine if you need the rabies vaccine for post-exposure protection. Though rare, rabies is a severe consequence worth discussing with a medical professional.
Psychological Effects
While rare, being scratched or bitten by a cat can have psychological effects on some people, especially children. One study published in the journal Biological Psychiatry found that being bitten or scratched by a cat before the age of 13 is associated with an increased risk of depression and self-harm later in life (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7239751/). The trauma of a cat attack, especially when young, can lead to the development of phobias, anxiety, stress, and PTSD in severe cases.
Another study in the journal PLoS ONE suggests there may be a link between cat scratches and the development of psychiatric disorders like schizophrenia, though more research is needed (https://nypost.com/2021/03/26/cat-scratch-bacteria-linked-to-schizophrenia-study/). While not everyone will experience psychological effects from a cat scratch, the trauma can be significant for some, especially children who may develop a lasting fear or phobia of cats.
Proper treatment, counseling, and support can help manage any psychological effects that emerge after a cat scratch or bite. Parents should watch for signs of anxiety, fear, or depression in children who have been injured by a cat and seek professional help if needed.
Risk Factors
According to the CDC, those most at risk for developing side effects from cat scratches are people with weaker immune systems, such as the elderly, pregnant women, and those with HIV/AIDS. These groups may have more difficulty fighting off infections from bacteria that can enter through a cat scratch.
People with allergies to cats are also at higher risk of side effects. Allergic reactions can range from mild itching and inflammation to potentially life-threatening anaphylaxis in those with severe cat allergies. Even a small cat scratch could introduce enough allergen to trigger a significant reaction in a highly allergic person.
Other risk factors include young children, who may not take proper care around cats and are more likely to get scratched. Stray and feral cats can also pose a greater risk, as they are more likely to carry diseases. Proper handwashing and care when interacting with cats can help reduce the risks of side effects from scratches.
Prevention
There are steps you can take to help prevent cat scratches and bites from becoming infected. According to the CDC, the most important prevention measure is proper handwashing.
Wash any cat scratches or bites with soap and running water right away. Scrub gently to remove any dirt or germs. Keep washing the area for at least 5 minutes. Do not allow cats to lick the wounds, as their saliva can introduce more bacteria.
Watch for signs of infection, including redness, swelling, warmth, pus, red streaks, enlarged lymph nodes near the scratch, and flu-like symptoms. See a doctor promptly if any of these develop, as antibiotics may be needed.
Cover minor scratches with clean bandages until fully healed. Keep the wound clean and change bandages regularly.
People with weakened immune systems, such as those with HIV/AIDS, should take extra care with cat scratches and consult a doctor at the first signs of infection.
Cats should be kept up to date on vaccines and flea/tick control to prevent the spread of infections. Declawing cats or trimming their nails can reduce potential scratches.
