Ear hematomas in dogs are caused by blood vessels rupturing inside the ear flap, and the most common trigger is repeated head shaking or intense ear scratching. The shaking and scratching are almost always a response to something else bothering the ear, which means the hematoma itself is usually a symptom of a deeper problem. Understanding what’s driving the behavior is the key to preventing it from happening again.
How Head Shaking Damages the Ear
The ear flap (called the pinna) is a thin sheet of cartilage sandwiched between two layers of skin, with small blood vessels running throughout. When a dog shakes its head hard or scratches at an ear repeatedly, those blood vessels can tear. Blood leaks out and pools between the cartilage and the skin, forming a fluid-filled swelling that can make the ear look like a puffy pillow or a water balloon. It typically happens fast, sometimes within hours of a bout of vigorous shaking.
Blunt trauma can cause the same thing. A knock during rough play, catching the ear on a fence or sharp object, or even running through dense brush can rupture a vessel and start the process. But trauma accounts for a small minority of cases. The overwhelming pattern is a dog that has been shaking or scratching because something in the ear is making it uncomfortable.
The Underlying Conditions That Start the Cycle
In a study of 59 ear hematomas across 49 dogs, 76% of cases had an active ear infection (otitis externa) at the time the hematoma developed. That makes ear infections the single biggest underlying cause. The remaining 24% had no obvious ear disease, but infections are so dominant in the data that any dog with a new hematoma should have its ears examined for signs of infection.
Beyond infections, several other conditions drive the head-shaking and scratching cycle:
- Allergies. Environmental allergens (pollen, dust mites) and food sensitivities cause itchy, inflamed ears. Dogs with chronic allergies often develop recurrent ear problems that set the stage for hematomas.
- Ear mites and parasites. These tiny organisms live in the ear canal and cause intense irritation, especially in puppies and dogs that spend time around other animals.
- Foreign bodies. A grass seed, foxtail, or bit of debris lodged in the ear canal creates immediate discomfort and frantic shaking.
- Chronic inflammation. Some dogs develop ongoing ear canal inflammation without a clear infectious cause, and the persistent irritation still triggers enough head shaking to cause damage over time.
If the underlying condition isn’t identified and treated, the hematoma is likely to come back even after it’s been drained or repaired. About 31% of dogs in one study developed multiple or new hematomas, often because the root cause was still present.
Why Certain Breeds Are More Vulnerable
Ear shape plays a significant role, but not in the way most people assume. Research from the Royal Veterinary College found that dogs with folded ears (the V-shaped drop ears you see on Labradors and Beagles) had twice the risk of hematomas compared to dogs with fully erect ears. Dogs with semi-erect ears had 1.6 times the risk. Surprisingly, dogs with long, pendulous ears (like Basset Hounds and Spaniels) actually had a slightly lower risk than average.
The RVC researchers proposed a new explanation for this pattern. Rather than head shaking being the sole cause, they suggest that repeated folding of the ear flap along a natural crease in the cartilage causes chronic damage and weakness along that fold line. Over time, this weakened cartilage is more likely to allow a bleeding episode. This “cartilage-folding hypothesis” helps explain why the condition clusters in breeds with certain ear shapes rather than simply in breeds prone to ear infections.
The breeds with the highest risk included Bull Terriers (7.4 times the risk of crossbred dogs), Saint Bernards (7.3 times), French Bulldogs (7.0 times), Irish Staffordshire Bull Terriers (5.5 times), and English Bull Terriers (5.4 times). Fourteen breeds total showed elevated risk compared to mixed-breed dogs.
The Role of Immune and Clotting Factors
Some veterinary researchers have noted that not every dog who shakes its head develops a hematoma, which suggests individual differences in blood vessel fragility or clotting ability may also play a role. Dogs on blood-thinning medications, dogs with clotting disorders, and older dogs whose blood vessel walls have become more fragile may be more susceptible to vessel rupture from the same amount of mechanical force. This hasn’t been as well studied as the infection and anatomy links, but it helps explain the cases where a hematoma appears without an obvious trigger or severe ear disease.
What Happens If a Hematoma Goes Untreated
A hematoma left alone will eventually be reabsorbed by the body, but the process is slow and painful. As the blood sits in the ear flap, it triggers significant inflammation that damages the surrounding cartilage and tissue. The result is a thickened, shrunken, permanently distorted ear, often described as “cauliflower ear.” Beyond the cosmetic issue, the scarring and deformation can actually obstruct the ear canal, making future ear infections more likely and creating a cycle of ongoing problems.
Hematomas are also genuinely painful. The pressure of trapped blood stretching the ear flap causes discomfort that makes the dog shake and scratch even more, which can enlarge the hematoma or cause new blood vessels to rupture. Early treatment breaks this feedback loop. Surgical drainage, where small holes are created to let the fluid escape and the tissue layers are held together while they heal, has a recurrence rate of only about 4%. Less invasive approaches like injection-based drainage carry a higher recurrence rate of around 33%, largely because the space tends to refill with fluid before the tissues can bond back together.
Preventing Ear Hematomas
Because the vast majority of hematomas trace back to ear discomfort, prevention comes down to keeping your dog’s ears healthy. Regular ear checks, especially after swimming or baths, help you catch infections early before the scratching and shaking become intense enough to cause damage. Dogs with allergies benefit from having their triggers managed, whether through diet changes or medication, since allergic ear inflammation is one of the most common chronic drivers.
For breeds with folded or semi-erect ears, pay extra attention to the ear flap itself. If you notice your dog frequently flipping or folding its ears during play or while lying down, that repeated cartilage stress may be contributing to long-term weakness in the tissue. Keeping ears dry, clean, and free of debris reduces the irritation that starts the head-shaking cycle. If your dog has already had one hematoma, treating any underlying ear disease aggressively is the most effective way to prevent a second one.