About 1 in 5 dog bites becomes infected, which makes them less infection-prone than you might expect. That overall rate of roughly 20% drops even lower for shallow wounds that are cleaned promptly, and rises significantly when bites involve certain body parts or when treatment is delayed.
How the Numbers Compare
The 3% to 18% infection rate commonly cited for dog bites sits well below the range for cat bites, which infect anywhere from 28% to 80% of the time. The difference comes down to wound shape. Dogs tend to crush and tear tissue, leaving relatively open wounds that are easier to clean. Cats puncture deeply with narrow teeth, pushing bacteria far below the skin where irrigation can’t easily reach.
Bites to the hand are a notable exception. About 36% of dog bites on the hand become infected, nearly double the overall rate. Hands have many small joints, tendons, and thin tissue layers with limited blood supply, all of which make it harder for your immune system to fight off bacteria. Bites to the feet carry similarly elevated risk. Facial bites, despite being common in children, actually tend to heal well because the face has excellent blood flow.
What Bacteria Are Involved
A dog’s mouth carries a complex mix of bacteria, and infected bites usually involve several species at once. The most common culprit is a group of bacteria called Pasteurella, found in roughly half of all dog bite wounds. Streptococcus and Staphylococcus species each show up in about 46% of cases. Various anaerobic bacteria (types that thrive in low-oxygen environments like deep puncture wounds) round out the mix.
One rare but dangerous organism worth knowing about is Capnocytophaga canimorsus, a bacterium that lives in the normal saliva of healthy dogs. In rare cases it can cause severe bloodstream infection with a mortality rate of approximately 30%. People without a spleen, heavy alcohol users, and those on immune-suppressing medications face the highest risk, but it can strike otherwise healthy people too.
Timing Makes a Major Difference
How quickly you clean and treat a dog bite has a dramatic effect on infection risk. One analysis found that bites treated within eight hours had an infection rate of just 4.5%, while those treated after eight hours jumped to 22.2%. That’s nearly a fivefold difference based on timing alone.
Once infection does take hold, symptoms typically appear within about 24 hours of the bite. In some cases, particularly with Pasteurella, signs can show up even faster, within 12 hours. For slower-developing infections like Capnocytophaga, symptoms can take up to 14 days to emerge.
Signs a Bite Is Getting Infected
The early warning signs are straightforward: increasing redness that spreads beyond the immediate wound edges, worsening swelling, warmth around the bite, and escalating pain rather than gradually improving pain. Pus or cloudy drainage from the wound is a clear signal. Red streaks extending away from the bite toward your torso indicate the infection is spreading along lymphatic channels, which needs prompt attention.
More serious systemic symptoms include fever, chills, muscle or joint pain, and in the case of Capnocytophaga infection, blisters around the bite, vomiting, diarrhea, headache, or confusion. Any of these signs appearing within two weeks of a bite warrant immediate medical evaluation.
Who Faces Higher Risk
Your personal health profile significantly shifts the odds. People with diabetes face elevated infection risk because high blood sugar impairs immune function and slows wound healing. Those taking immunosuppressive medications (for autoimmune conditions, organ transplants, or cancer treatment) are similarly vulnerable. People who have had their spleen removed are at particular risk for the dangerous Capnocytophaga infections.
Beyond health conditions, wound characteristics matter. Deep puncture wounds are harder to clean than surface-level tears. Bites that crush tissue create pockets of damaged cells where bacteria thrive. And as noted, location on the body plays a role: hands, feet, and areas over joints carry higher risk than fleshy areas like the upper arm or thigh.
How Cleaning Reduces Your Risk
Thorough wound irrigation is the single most effective step for preventing infection. High-pressure rinsing with clean water physically flushes bacteria out of the wound before they can establish themselves. For a practical approach at home, running clean tap water over the wound for several minutes, or using a squeeze bottle to create gentle pressure, removes the majority of contaminants.
This initial cleaning is why the overall infection rate stays as low as 20%. Superficial bites that are washed well in a healthy person rarely need anything beyond basic wound care. Current infectious disease guidelines recommend preventive antibiotics only for high-risk situations: bites to the hands, feet, or face, deep puncture wounds, bites in people with diabetes or weakened immune systems, and wounds that weren’t cleaned within that critical eight-hour window. When preventive antibiotics are prescribed, a three-to-five day course is the standard recommendation.
Despite these targeted guidelines, studies show that antibiotics are prescribed far more liberally in practice. One pediatric study found that 91.5% of all dog bites received an antibiotic prescription, regardless of risk level. Whether that over-prescribing helps or simply adds unnecessary medication is an ongoing point of discussion among emergency physicians.