One ear standing up while the other flops down is usually harmless, especially in puppies and young dogs whose ear cartilage is still developing. In adult animals, though, a sudden change to asymmetrical ears can signal an ear infection, injury, or nerve problem worth investigating. The meaning depends heavily on the animal’s age, breed, and whether the droopy ear is new.
Puppies Growing Into Their Ears
The most common reason for one ear up and one ear down is simple: the ears haven’t finished developing yet. In breeds that are supposed to have erect ears (German Shepherds, Huskies, Corgis, and others), the cartilage in each ear stiffens at its own pace. One ear often stands up weeks before the other catches up. This is completely normal and can last anywhere from a few weeks to several months.
Most puppies have their full adult ear carriage by about six to seven months, though some larger breeds take longer. During teething, which runs roughly from three to six months, ear cartilage can temporarily soften because the body redirects calcium and other resources toward growing teeth. You might see ears that were standing fine suddenly flop again, or one ear go up while the other drops. Once teething wraps up, the ears typically settle into their final position.
Breed-Specific Ear Types
Not every breed is meant to have matching upright ears. The American Kennel Club recognizes a range of ear types that can make asymmetry look more dramatic than it is. Semi-prick ears, for instance, stand erect with just the tips leaning forward. Button ears have a flap that folds forward over the ear opening. Rose ears fold over and back, exposing part of the inner ear canal.
Breeds with semi-prick or button ears (Collies, Jack Russell Terriers, Fox Terriers) sit in a gray zone where one ear might prick up fully while the other holds its fold. This isn’t a health issue. It’s a variation in how strongly the cartilage supports the ear tip. Many owners and breeders consider the look charming, and for mixed-breed dogs that inherit ear traits from different parents, a mismatched look is even more common.
Ear Infections and Aural Hematomas
When an adult dog or cat suddenly develops one droopy ear after years of symmetrical ears, an ear problem is the first thing to consider. Ear infections cause pain, itching, and swelling inside the ear canal, which can make the animal hold the affected ear lower or tilted to one side. You’ll often notice head shaking, scratching at the ear, redness, odor, or dark discharge.
Persistent head shaking and scratching can lead to a secondary problem called an aural hematoma, a blood-filled swelling on the ear flap. This happens when vigorous shaking ruptures small blood vessels between the skin and cartilage of the ear. The ear flap fills with fluid, becomes puffy and heavy, and droops under its own weight. In the early stages, the swollen area feels warm and the skin looks reddened. Left untreated, the fluid eventually reabsorbs on its own, but the resulting scar tissue contracts and permanently crumples the ear into a thickened, misshapen “cauliflower ear.” Veterinary treatment early on preserves the ear’s normal shape.
Aural hematomas are far more common in dogs than cats, and they usually affect just one ear, which is exactly the scenario that creates the one-up-one-down look in a dog that previously had matching ears.
Nerve Damage and Facial Paralysis
A less common but more serious cause is facial nerve paralysis. The facial nerve runs very close to the inner ear, so any infection or inflammation in the middle or inner ear can damage it. When that nerve stops working properly on one side, the muscles that hold the ear in position lose their tone. The ear droops, and the dog may also be unable to blink on that side or may have a drooping lip.
These signs appear suddenly. Other possible causes of facial nerve damage include physical injury, thyroid disease, generalized nerve disorders, immune-mediated conditions, and rarely tumors. If your dog’s ear drops overnight and you also notice a drooping eyelid, drooling from one side of the mouth, or difficulty eating, those are signs of nerve involvement rather than a simple ear infection.
Rabbits and Cats
Rabbits with one lop ear and one upright ear are surprisingly common, particularly in breeds that carry both lop and erect ear genetics. “Half-lop” or “helicopter ears” often show up in mixed-breed rabbits and are a normal genetic trait. However, lop-eared rabbits are significantly predisposed to ear disease compared to erect-eared rabbits. A large field study found that lop-eared rabbits had higher rates of abnormal ear canal color, ear canal narrowing, various types of discharge, and behavioral signs of discomfort during ear exams. So if a rabbit that normally holds both ears the same way starts dropping one, an ear infection (otitis externa) is worth ruling out.
In cats, asymmetrical ears are less common but follow similar logic. Ear mites, infections, and hematomas can all cause one ear to droop. Scottish Folds naturally have folded ears due to a cartilage gene, and in some individuals the fold affects one ear more than the other, creating a mismatched appearance.
How to Tell Normal From Concerning
A few patterns help sort out when one ear up and one ear down is just a quirk versus something that needs attention:
- Age matters most. In animals under a year old, asymmetrical ears that have been that way for weeks are almost always developmental. The cartilage is still firming up.
- Sudden changes are the red flag. An adult animal whose ears were symmetrical yesterday but aren’t today likely has pain, swelling, or nerve involvement in the droopy ear.
- Look for secondary signs. Head tilting, scratching, odor, discharge, swelling of the ear flap, or facial drooping on the same side all point toward a medical cause.
- Check the ear flap. A puffy, fluid-filled ear flap that feels like a small water balloon suggests a hematoma. A hot, red ear canal suggests infection.
For puppies in the middle of teething, adequate nutrition supports cartilage development, but there’s no reliable way to force an ear to stand up faster. Taping methods exist in some breeding communities, but results are inconsistent and the ear usually does what genetics dictate regardless. If a puppy’s ear is still down past eight or nine months, it will likely stay that way, which is purely cosmetic and causes no health problems.