Cat scratches often produce an intense, lingering itching sensation. This reaction is more complex than a simple response to skin trauma, involving the mechanics of the cat’s claw, the proteins it deposits, and the potential for introducing microbial invaders.
How Cat Claws Deliver Foreign Substances
A cat’s claw is designed to grip and puncture tissue, not create a clean cut. Composed of keratin, the claw tapers to a fine, curved point that easily breaks the skin barrier. Its curved shape pulls and tears tissue as it is withdrawn, often resulting in a puncture or a ragged channel reaching into the dermis.
This mechanical action drives materials deep into the wound track. The claw’s surface is rarely sterile, often harboring microscopic debris from the cat’s environment, such as the litter box or outdoor soil.
The Immune System’s Reaction to Cat Proteins
The most immediate and intense itching is often an allergic reaction to proteins deposited by the cat. Cats produce a potent allergen called Fel d 1, a protein complex found primarily in their saliva and sebaceous glands. When a cat grooms itself, this protein transfers onto the fur and subsequently onto the claws.
A scratch injects these foreign proteins directly into the skin, triggering an immediate immune response. The immune system misidentifies Fel d 1 as a harmful invader, prompting specialized cells to produce Immunoglobulin E (IgE) antibodies specific to the allergen.
These IgE antibodies attach to mast cells residing in the skin. When Fel d 1 binds to the IgE, it signals the mast cell to release inflammatory mediators like histamine. Histamine is responsible for the classic allergic symptoms of localized redness, swelling, and persistent itching.
The Risk of Bacterial Contamination
Beyond the immediate allergic itch, a cat scratch introduces a significant risk of bacterial contamination. A cat’s mouth and claws naturally harbor various pathogens that are inoculated into the wound.
One relevant threat is Bartonella henselae, the causative agent of Cat Scratch Disease (CSD). Cats, especially kittens, become infected through flea bites; the bacteria then adheres to the cat’s fur and claws via flea excrement. When the skin is broken, the bacteria is implanted.
Symptoms of CSD often begin 3 to 14 days after injury with a small lesion, potentially followed by fever, fatigue, and headache. The hallmark is the painful swelling of lymph nodes (lymphadenopathy) closest to the scratch site.
This condition represents a true microbial infection, distinct from the immediate itch. Common bacteria like Staphylococcus and Pasteurella multocida, found in the cat’s oral flora, can also be introduced, potentially causing cellulitis or localized infections.
Treating the Scratch and Monitoring Symptoms
Immediate attention to a cat scratch is necessary to minimize infection risk and reduce discomfort. The area should be thoroughly washed with soap and running water for at least five minutes to remove foreign debris and bacteria. Applying an over-the-counter antiseptic or antibiotic ointment after cleaning provides protection against microbial growth.
Topical anti-itch creams containing hydrocortisone can help soothe inflammation and histamine-driven itching. Oral antihistamines may also reduce the allergic response to deposited cat proteins.
If the wound shows signs of worsening infection, seek medical attention promptly. Signs requiring professional evaluation include increasing redness, warmth, swelling, or pus. A persistent fever, flu-like symptoms, or tender, swollen lymph nodes lasting more than 48 hours also flag potential bacterial infections like CSD.