A dog does not bite a cat once. It catches, lifts and shakes, and one 2-second shake drives 3 to 6 canine punctures through skin, fat and muscle. Each hole is 2 to 4 mm across and the tract beneath it runs 5 to 15 mm deep, so the wound that looks like a scratch is the one that becomes a febrile, anorexic cat 48 hours later. Flush a full 10 minutes, get a prescription antibiotic started inside 24 hours, and leave every hole open.
One bite, 3 to 6 holes, and none of them line up
A medium dog carries upper and lower canines 1.5 to 2 cm long. The cat's skin slides 5 to 20 mm over the muscle before it tears, so the surface hole and the deep tear rarely sit on the same line. A 2 mm scab can roof a 3 cm pocket of crushed fat. Crush injury matters more than the cut itself: a 20 to 30 kg jaw leaves a 3 to 5 mm rim of tissue without blood supply around every tract, and that dead rim is where Pasteurella and anaerobes multiply. Do not probe with a cotton bud, do not squeeze to see whether pus appears, and do not close the skin. In practice about 8 of 10 sutured cat bite wounds form an abscess between 24 and 72 hours, while an open, flushed wound usually resolves in 7 to 10 days.
Three puncture classes decide volume and speed
Vets sort a dog bite on a cat by depth and by what lies under the hole, not by how dramatic it looks. The class sets how much fluid you push and how fast you drive.
| Class | Depth (mm) | Holes | Flush (mL) | Vet within (h) |
|---|---|---|---|---|
| 1, skin only | 2 to 5 | 1 to 2 | 250 | 24 |
| 2, fat and muscle | 5 to 20 | 3 to 4 | 500 | 6 |
| 2b, joint or limb | 10 to 30 | 2 to 6 | 500 to 750 | 4 |
| 3, chest wall | 15 to 40 | 2 to 6 | 750 | 1 |
| 3b, abdomen | 20 to 50 | 1 to 4 | 1000 | 1 |
Class 3 means a canine crossed the rib line or the abdominal wall, and it is a same-hour problem even if the cat walks. Roughly 1 in 5 chest bites leaves air in the pleural space; a resting respiratory rate above 40 per minute, a 2 cm strip of flank that moves differently from the other side, or gums that go pale 30 minutes after the bite all point the same way.
Ten minutes of flushing, with a clock running
Ten minutes is 600 seconds and it feels absurdly long over a 3 mm hole. That duration is the point: a 5-second rinse moves surface debris and nothing else, while 600 seconds of low-pressure flow dilutes the bacteria pushed into the tract. Use a 20 mL syringe with an 18 gauge needle, or a 35 mL syringe with a 19 gauge, and 250 to 500 mL of 0.9% saline at 20 to 25 C. Tap water at the same temperature works if saline is not in the house. Clip 2 cm of fur around every hole first, because fur holds 5 to 10 times its weight in fluid and keeps bacteria pressed against the skin. Aim the stream at 45 degrees into the hole rather than straight down, and count each tract separately: 3 holes means 3 passes of 150 to 200 mL. Skip hydrogen peroxide, alcohol and iodine inside a puncture. All 3 damage the tissue you are trying to save and can stretch healing from 7 days to 14.
Antibiotics inside 24 hours, by prescription only
Dog mouth flora in a cat wound is a mix of Pasteurella multocida, Staphylococcus, Streptococcus and anaerobes, and a 5 kg cat has little reserve against it. Most vets choose a beta-lactam such as amoxicillin-clavulanate, or clindamycin when penicillin is a problem, for 7 to 10 days. The drug, the dose and the course come from a veterinary prescription after an exam, never from a leftover strip in a cupboard. A human tablet split by eye under-treats a 5 kg cat and selects resistance. Aim for the first dose at hour 2 to 8 rather than hour 23; the 24-hour mark is the outer limit, not the target. Never give ibuprofen, acetaminophen, aspirin or naproxen: 1 adult ibuprofen tablet can cause acute kidney injury in a 4 kg cat, and 1 acetaminophen tablet can cause methemoglobinemia.
The 48-hour watch: measure, do not look
Photograph the wound beside a ruler at hour 0 and mark the swelling edge with a pen and the time. Then measure at 12, 24, 36 and 48 hours along the same 2 axes. An edge that moves outward by 5 mm in 12 hours, skin 2 C warmer than the matching spot on the other side, or a rectal temperature above 39.5 C means a pocket is forming. Most abscesses point between 24 and 72 hours; they need drainage, another flush and 7 to 10 days of antibiotics. A temperature above 40 C, 24 hours without food, or a limp that worsens at hour 36 is a same-day visit, not a tomorrow visit.
Rabies, tetanus and the 72-hour clock
A cat bitten by a dog of unknown vaccination status is a category 3 exposure. Rabies vaccine goes in within 72 hours, with immunoglobulin infiltrated around the wounds, and the cat stays under observation. Write down the dog owner's name, phone number, a photo of the vaccination card, the exact time and the location within 100 m, because animal control will ask for all 5. Most jurisdictions want the bite reported within 24 hours. Tetanus is rare in cats, but a 20 mm tract contaminated with soil is the classic setup, and a booster decision belongs to the vet.
Red flags that skip the waiting room
Red flags are a resting rate outside 20 to 40 per minute, gums that read pale, grey or blue, a gum press that takes longer than 2 seconds to pink back up, a heart rate past 220 (normal 140 to 220), any collapse, bleeding from a nostril, or an abdomen that is tight and 2 cm wider than 6 hours ago. Any 1 of those means drive now, with the wound covered by a clean dry pad and nothing else.
The first 60 minutes, in order
- Press a clean pad on the bleeding hole for 5 minutes without lifting it once.
- Clip 2 cm of fur around every hole, then flush 250 to 500 mL across a full 10 minutes.
- Cover with a loose non-stick pad only. No compression bandage, no glue, no stitches.
- Call the clinic, say 3 to 6 punctures from a dog bite, and ask for a slot inside 6 hours.
- Photograph with a ruler and start the 12-hour measurement log.
- Withhold food for 4 hours in case sedation is needed; water stays available.
If the cat is also losing blood, follow the pressure and packing steps in bleeding and wounds. If the dog was guarding bait or the cat ate something at the scene, run the substance through the toxin lookup before you leave.
Terms mentioned in this article
Frequently asked
The holes are tiny and the cat is eating. Can I just watch it for a day?
Watch it only after a 10-minute flush. A 3 mm surface hole can roof a 30 mm pocket of crushed fat, and roughly 8 of 10 unflushed bite wounds form an abscess between 24 and 72 hours. Flush 250 to 500 mL, photograph the wound beside a ruler, then measure the swelling at 12, 24, 36 and 48 hours. Any edge that grows 5 mm in 12 hours, or a rectal temperature above 39.5 C, means a same-day visit.
Can I use hydrogen peroxide or alcohol to clean the punctures?
No. Both damage the tissue you are trying to save and push healing from about 7 days to 14. Use 0.9% saline or tap water at 20 to 25 C, delivered with a 20 mL syringe and an 18 gauge needle at a 45 degree angle, 150 to 200 mL per tract. Clip 2 cm of fur around each hole first, because fur holds 5 to 10 times its weight in fluid and keeps bacteria against the skin.
Do all dog bites on cats need antibiotics?
Most vets treat deep punctures, any bite over a joint, and every bite in a cat with a fever as an antibiotic case, usually 7 to 10 days of a beta-lactam or clindamycin on prescription. A single shallow 2 mm graze in a healthy cat may only need flushing and a 48 hour check. The decision needs an exam, so call inside 6 hours rather than deciding at home.