That sharp, onion-like smell coming from your rabbit is almost certainly buildup in their inguinal scent glands. These small glands sit on either side of your rabbit’s genitals and produce a waxy secretion that can accumulate, harden, and give off a surprisingly pungent odor. The good news: it’s normal, fixable, and rarely a sign of anything serious.
Scent Gland Buildup Is the Most Common Cause
Rabbits have inguinal glands that produce secretions used for marking territory and identifying group members. These secretions carry chemical signatures so specific that other rabbits can tell a stranger from a companion based on the scent alone. In the wild, this system helps maintain social structure. In your home, it mostly just produces a smell that many owners describe as onion-like or sulfurous.
The secretion itself is a dark, waxy substance that accumulates in small folds of skin flanking the genital area. When it builds up over weeks, it hardens and intensifies, shifting from a mild musk to something much sharper. Some rabbits produce more than others, and overweight rabbits or those with limited mobility tend to accumulate it faster because they can’t groom the area effectively. If you’ve never cleaned your rabbit’s scent glands, this is very likely the source of the smell.
How to Clean the Glands
You should check your rabbit’s scent glands about once a month. Hold your rabbit securely with good back support (a towel-wrapped “bunny burrito” works well) and gently part the fur around the genital area. You’ll see two small pockets, one on each side. If there’s dark, waxy buildup inside, that’s the problem.
Dip a cotton swab in warm water or baby oil and gently swab out the buildup. It may take a few passes. The substance can be sticky and hardened, so don’t rush. If the glands look red, swollen, or irritated beyond normal buildup, the area may be infected and needs veterinary attention. Once cleaned, the onion smell should disappear within a day or so.
Intact Rabbits Smell Stronger
If your rabbit hasn’t been spayed or neutered, hormones significantly amplify their overall scent. Intact males in particular produce a musky odor once they hit sexual maturity, and their urine and fecal pellets carry a noticeably stronger smell than those of neutered rabbits. Males may also spray urine to mark territory, which adds another layer to the problem.
Spaying or neutering reduces both the intensity of scent gland secretions and the odor of urine and droppings. If your rabbit is intact and the onion smell seems to be everywhere rather than localized to one spot, hormonal scent production is likely compounding whatever gland buildup is present.
Could It Be Something Your Rabbit Ate?
If your rabbit actually got into onions, garlic, leeks, or similar plants, you’d have a different kind of problem. These foods contain sulfur compounds that break down into chemicals responsible for that classic onion smell. In dogs and cats, onion ingestion causes an onion odor on the breath along with potentially serious damage to red blood cells.
Rabbits are somewhat more resistant to one of the key toxic compounds in onions because of how their digestive system processes it. But “more resistant” doesn’t mean safe. Onions, garlic, and other plants in the allium family are still considered toxic to rabbits and should never be offered. If you suspect your rabbit chewed on any of these foods, watch for signs of lethargy, loss of appetite, or changes in droppings, and contact your vet.
That said, dietary causes are rare simply because most rabbit owners don’t feed alliums. If you haven’t offered anything unusual and your rabbit’s breath smells fine up close, the scent glands are the far more likely explanation.
Dental Disease and Other Medical Causes
A strong, foul odor coming specifically from your rabbit’s mouth points toward dental problems rather than scent glands. Rabbits’ teeth grow continuously throughout their lives, and when teeth become overgrown or misaligned, food can pack into gaps, bacteria thrive, and abscesses can form. The result is noticeably bad breath that some owners describe as sharp or sulfurous.
Other signs of dental disease include drooling, difficulty eating, dropping food, weight loss, or a wet chin. If the onion-like smell seems concentrated around your rabbit’s face rather than their back end, a dental exam is worth pursuing. Chronic dental disease in rabbits is progressive and typically requires professional treatment to manage.
Narrowing Down the Source
The fastest way to figure out what’s going on is to locate where the smell is strongest. Pick up your rabbit and sniff near the back end versus the face. If the smell is strongest around the genital area, check and clean the scent glands. If it’s coming from the mouth, dental issues are more likely. If the smell seems to come from the urine or the whole body, consider whether your rabbit is intact and whether their litter box is being cleaned frequently enough.
Most of the time, a quick gland cleaning solves the mystery entirely. Owners are often surprised by how much odor those two tiny glands can produce, and how quickly the smell vanishes once the buildup is removed.