A hematoma on a dog is a pocket of blood that collects between layers of tissue, usually caused by broken blood vessels beneath the skin. The most common type by far is an aural hematoma, a soft, fluid-filled swelling on the ear flap. It looks like a puffy pillow or balloon forming inside the ear, and it can appear suddenly, sometimes within hours. While hematomas can technically form anywhere on a dog’s body, the ear is the location that sends most owners to a search engine, so that’s where we’ll focus.
How Ear Hematomas Form
The ear flap (pinna) has a thin layer of cartilage sandwiched between two layers of skin, with tiny blood vessels running throughout. When a dog shakes its head hard or scratches at its ear aggressively, those small blood vessels can rupture. Blood leaks out and pools in the space between the cartilage and the skin, and because there’s nowhere for it to drain, it creates a warm, squishy swelling that can range from a small marble-sized bump to a ballooning that fills nearly the entire ear flap.
The swelling itself isn’t the root problem. Something is making the dog shake or scratch in the first place, and that’s what ultimately needs to be identified.
What Causes the Shaking and Scratching
Most dogs that develop an aural hematoma have an underlying ear condition driving the behavior. The most common culprits are ear infections (bacterial or yeast), allergies, ear mites, and foreign material lodged in the ear canal like a tick, grass seed, or foxtail. Sometimes the foreign object has already fallen out by the time you notice the swelling, but it triggered enough irritation to start a cycle of head shaking that damaged the blood vessels.
Bite wounds from other animals can also cause hematomas directly through blunt trauma to the ear. Less commonly, dogs with a bleeding or clotting disorder may develop an aural hematoma without much trauma at all. If your dog develops hematomas easily or in unusual locations, that’s worth investigating further.
What It Looks and Feels Like
A fresh hematoma feels like a warm, squishy water balloon on the ear flap. The ear may hang lower than normal from the weight of the fluid, and your dog will likely tilt their head to one side. The area is typically tender, so your dog may flinch or pull away when you touch it. Over the following days, the fluid can begin to clot, making the swelling feel firmer and less uniform.
You might also notice your dog continuing to shake their head, paw at the ear, or rub it along furniture and the floor. These are signs the underlying irritation is still active, and ongoing shaking can make the hematoma larger or prevent it from healing.
How Veterinarians Diagnose It
The hematoma itself is usually obvious on a physical exam. What matters more is figuring out why it happened. Your vet will likely look inside the ear canal for signs of infection, mites, or foreign material. A fine needle aspirate, where a small needle draws out a sample of the fluid, confirms it’s blood rather than something else like an abscess or tumor. Depending on the situation, additional testing may include ear swabs to identify the type of infection, allergy testing, or bloodwork to check for clotting problems or hormonal conditions that affect skin and ear health.
Treatment Options
There are two main approaches: draining the fluid with a needle, or surgery. Simple needle drainage is the less invasive option. A vet inserts a needle into the swelling, draws out the blood, and sometimes injects a small amount of medication to reduce inflammation. The problem is that the empty space often refills with blood, sometimes within days. Many dogs need repeated draining, and some never fully resolve this way.
Surgery is the more definitive fix. The vet opens the hematoma, removes the clotted blood, and places several small stitches through the ear flap to hold the skin and cartilage back together so the pocket can’t refill. A small drainage tube may be placed to let any new fluid escape during healing. The tube is typically removed between 3 and 14 days after the procedure, depending on how well the ear is healing.
After surgery, most dogs wear an Elizabethan collar (the cone) to prevent scratching, and the ear is often bandaged against the head to keep it still. Full recovery takes about two weeks.
What Happens Without Treatment
A hematoma won’t kill your dog, but leaving it untreated leads to a predictable outcome. The body eventually reabsorbs the blood on its own over several weeks, but as it does, scar tissue forms unevenly throughout the ear flap. The cartilage contracts and crumples, leaving the ear permanently thickened, shrunken, and wrinkled. This is sometimes called “cauliflower ear,” the same thing wrestlers and boxers get. Beyond the cosmetic issue, the scarred, narrowed ear canal can trap moisture and debris, making future ear infections more likely.
Equally important, if the underlying condition goes unaddressed, your dog may keep shaking and scratching, either worsening the existing hematoma or creating new ones on the same or opposite ear.
Hematomas in Other Locations
While ear hematomas get the most attention, dogs can develop hematomas elsewhere. A bump or swelling under the skin after a hard knock, a fall, or rough play could be a hematoma. These typically resolve on their own as the body reabsorbs the blood, though larger ones may need to be drained.
Internal hematomas are a more serious matter. Blood collecting around organs like the spleen or liver often produces no obvious signs in the early stages. When symptoms do appear, they tend to come on suddenly: acute weakness, collapse, pale gums, or a distended belly. Internal bleeding can result from trauma (like being hit by a car) or from ruptured masses on organs. These situations are emergencies that require immediate veterinary care.
Preventing Recurrence
The single most important thing you can do is treat whatever is making your dog shake or scratch. If it’s an ear infection, that means completing the full course of treatment rather than stopping when the ear looks better. If allergies are the trigger, working with your vet on long-term management keeps the ears from becoming chronically inflamed.
Routine ear checks at home help you catch problems early, before they escalate to the point of head shaking. Look for redness, discharge, odor, or debris in the ear canal. Dogs with floppy ears, dogs that swim frequently, and breeds prone to allergies are at higher risk and benefit from more regular monitoring. If your dog starts shaking their head frequently or pawing at an ear, that’s worth a vet visit before it turns into a hematoma.