An infected cat scratch typically shows increasing redness, swelling, warmth, and pain around the wound in the days after the injury. You may also notice pus or cloudy discharge, a small raised bump at the scratch site, or swollen lymph nodes in the weeks that follow. Knowing which signs are normal healing and which point to infection can help you decide whether you need medical attention.
Normal Healing vs. Early Infection
Some redness and mild swelling right after a cat scratch is completely normal. Your skin is reacting to the physical damage, and that initial inflammation usually fades within a day or two. What you’re watching for are signs that get worse instead of better.
An infected scratch will show redness that spreads outward from the wound rather than shrinking. The area around it may feel noticeably warm to the touch and become increasingly painful or tender, even when you’re not bumping it. Swelling that grows over several days instead of going down is another clear signal. If you see pus, whether it’s white, yellow, or greenish discharge oozing from the scratch, that’s a strong indicator that bacteria have taken hold.
A small raised bump (called a papule) or a blister filled with fluid may also appear right at the scratch site. This is one of the hallmark signs of cat scratch disease, an infection caused by bacteria that live in cats’ saliva and on their claws. Anywhere from 4% to 70% of cats carry these bacteria, depending on the region and whether they’re indoor pets or strays. Kittens are more likely carriers than adult cats.
Signs the Infection Is Spreading
The most telling sign that a cat scratch has progressed beyond a simple skin infection is swollen lymph nodes. These are the small, bean-shaped glands in your neck, armpits, and groin that filter bacteria. With cat scratch disease, the lymph nodes closest to the scratch become enlarged and tender, typically 1 to 3 weeks after the injury. A scratch on your hand or arm, for example, might cause a swollen, sore lump in your armpit. These swollen nodes can range from the size of a grape to a golf ball and sometimes take weeks or even months to return to normal.
A low-grade fever is another systemic sign. You might also feel generally tired or run down, similar to a mild flu. On their own these symptoms aren’t an emergency, but they do mean your body is fighting a real infection and you should see a healthcare provider for evaluation.
Red Flags That Need Immediate Attention
Certain signs mean the infection is moving fast and you shouldn’t wait for a regular appointment. Red streaks extending outward from the scratch along your skin are the hallmark of a condition called lymphangitis, where infection has entered the lymphatic vessels. This can spread quickly through the body.
Other urgent warning signs include:
- High fever with chills, not just a mild temperature elevation
- Rapidly expanding redness that visibly grows over hours
- Severe headache or confusion
- A wound that won’t stop oozing or develops a foul smell
These symptoms can indicate the infection has entered your bloodstream. In rare cases, cat scratch disease can lead to serious complications affecting the heart, liver, brain, or bones. This is uncommon in otherwise healthy people, but it does happen, and prompt treatment makes a significant difference.
Who Faces Higher Risk
Most cat scratch infections in healthy adults are self-limiting, meaning your immune system eventually clears the bacteria without treatment. But certain groups face a much higher chance of severe illness. People with weakened immune systems, whether from conditions like HIV, cancer treatment, or organ transplant medications, can develop life-threatening complications including septic shock. About 5% of cat scratch disease cases present with atypical, systemic symptoms affecting the spleen, skin, eyes, or nervous system, and immunocompromised individuals are overrepresented in that group.
Children under 5, adults over 65, and pregnant women are also considered higher risk. If you fall into any of these categories and get scratched by a cat, it’s worth having the wound evaluated even before obvious signs of infection appear.
First Aid Right After a Scratch
Proper cleaning immediately after a cat scratch significantly lowers your infection risk. Start by rinsing the wound under clean running water to flush out bacteria. Be gentle here; scrubbing aggressively can push bacteria deeper into the tissue. Next, wash the area thoroughly with soap and water. If you have an over-the-counter antibiotic ointment, apply a thin layer. Then cover the scratch with a clean bandage.
Keep the wound clean and dry in the days that follow, changing the bandage daily or whenever it gets wet or dirty. This simple routine prevents most cat scratches from becoming infected in the first place.
How Cat Scratch Disease Is Diagnosed
There’s no single definitive test for cat scratch disease. Doctors typically piece together a diagnosis from your history of cat contact, a physical exam showing the characteristic bump at the scratch site and swollen lymph nodes, and sometimes blood tests that look for antibodies against the bacteria. An antibody level above a certain threshold is considered diagnostic, though sensitivity varies between tests.
In uncertain cases, a DNA-based test on tissue samples can confirm the bacteria’s presence with near-perfect accuracy, though it occasionally misses infections. Sometimes the diagnosis comes down to ruling out other causes of swollen lymph nodes and checking whether at least two supporting criteria are met: positive blood work, tissue samples showing a specific pattern of inflammation, and a history of cat exposure.
For healthy individuals, treatment is often just monitoring and symptom management while the infection runs its course. For immunocompromised patients, antibiotics are a critical part of treatment and can be the difference between a manageable illness and a dangerous one.