Can Dogs Eat Onions? What to Know About Onion Toxicity in Dogs

By: Dr. Juli, DVM

Many home chefs and foodies keep their kitchens stocked with flavorful spices and staples, like onions, to complete their favorite dishes. Onions and onion flavorings complement various dishes and are popular stand-alone foods that can be enjoyed fried, grilled, or raw. It’s not uncommon to want to share your plate with your pet. However, many human foods, especially onions, and other Allium family members, can be deadly to dogs.

While it may be tempting to season your pup’s treats or food, it’s critical to understand which human foods are safe for dogs to prevent an unexpected illness, some of which can be lethal. In fact, human foods, including grapes, raisins, garlic, and onions, are among the top 10 most reported pet toxins, according to the ASPCA Animal Poison Control Center.

Understanding the risks and what to do if your pup accidentally ingests onions or an onion-flavored food will help prevent a potentially devastating illness in your dog.  

Are Onions Safe for Dogs?

Onions and any Allium spp. are not safe for dogs. Never feed your dog onion powder, onion rings, onion soup, leeks, chives, shallots, red onions, sweet onions, white onions, green onions, garlic, or garlic powder. Additionally, garlic is three to five times more toxic than onions.

All parts of the onion or other Alliums, including the leaves, are toxic to pets, and cooking does not reduce the toxicity. Alliums, including onions, contain the poisonous compound N-propyl disulfide, which can damage a dog’s red blood cells, causing them to burst or hemolyze. This red blood cell destruction results in fewer red blood cells (i.e., hemolytic anemia) available to transport oxygen throughout your dog’s body to support organ function.

Affected dogs are at risk of kidney damage, urine discoloration, collapse, and death. Some dog breeds have an increased sensitivity to onion ingestion and are more at risk for severe illness, including Akitas, Shiba Inus, and dogs with underlying liver or kidney disease.

Common Sources of Onion Poisoning in Dogs

Onions, including flavorings and powders, are used in various foods, including eggs, meats, sauces, and soups. Onions and garlic powders may also be included in some human supplements. Always check the label before offering your dog any human food.

Feeding your dog chicken or bone broth can help boost its nutrition or encourage a picky eater. However, many human broths and soups contain onion and garlic flavorings. Giving your dog a veterinary-formulated broth, like Native Pet Bone Broth, will ensure it is not at risk for accidental poisoning. The tempting onion aroma can be challenging for canine companions to resist, so keep your dog out of the kitchen when cooking with onions. Small amounts of onion can be toxic for dogs and have devastating consequences for their health. 

Signs of Onion Toxicity in Dogs

Symptoms of onion toxicity depend on the amount ingested, a dog’s weight, and underlying health issues. Generally, dogs who ingest 0.5% of their body weight in onions are at risk for toxicity signs.

Additionally, onion powder is more concentrated, so small amounts can have toxic effects. Clinical signs occur within 24 hours following a dog’s ingestion of a large amount of onion. However, more severe illness signs can take several days to be evident.

Onion toxicity signs may include:

• Vomiting
• Diarrhea
• Decreased appetite
• Lethargy
• Constipation
• Excess drooling
• Increased panting
• Elevated heart rate
• Abdominal pain
• Increased or decreased thirst
• Increased or decreased urination
• Red-tinged urine
• Pale gums
• Loss of balance
• Exercise intolerance 

What to Do if Your Dog Ate Onion Products

Seek immediate veterinary care if you observe or suspect your dog has ingested onions, a food with onion flavoring, or other Allium spp., like garlic. In some cases, it may not be cause for concern, but because it may take days for severe effects to occur, it’s better to be safe than sorry.

The Pet Poison Helpline, or the ASPCA Animal Poison Control Center, can also help pet owners determine if immediate emergency veterinary care is required, especially if the incident occurs when your family veterinarian is closed. In some cases, your veterinarian may advise you to induce your dog to vomit at home, but never attempt this unless directed by your DVM. 

Onion Toxicity Diagnosis and Treatment

An onion poisoning diagnosis is based on a history of ingestion, clinical signs, and blood work findings. Affected dogs may have a low red blood cell count and elevated kidney values. Early decontamination, within a few hours of ingestion, will give affected dogs the best chance to avoid severe illness.

Your veterinarian will likely induce your dog to vomit, followed by activated charcoal to help decrease onion absorption. Dogs with more severe cases or abnormal blood work may require hospitalization for supportive care and monitoring.

There is no antidote for onion toxicity. Treatment may include:

• Intravenous fluids 
• Anti-nausea medication
• Oxygen supplementation
• Blood transfusions

Affected dogs will require several veterinary checkups and blood work monitoring for several weeks following onion poisoning since the effects on the organs can be long-lasting. 

How to Prevent Onion Toxicity

Always read the label and check with your veterinarian before offering your dog any human foods, supplements, or treats. Vegetables can be an excellent treat for your pup, but ensure they are unseasoned, dog-safe veggies like the ones listed here. Accidents can happen anytime, especially if your dog enjoys dumpster diving and counter-surfing.

Follow these tips to prevent an accidental onion toxicity:

• Pet-proof kitchen cabinets and garbage cans.
• Never share your dinner plate with your pet.
• Provide dog-friendly treats and enrichment, like Native Pet Yak Chews, especially when cooking with onions or Allums.
• Fence off gardens containing Allium family members (i.e., garlic, chives, leeks, onions).
• Check your yard and remove any wild onions.

Onions are a flavorful addition to many human dishes, but this popular vegetable can be deadly for dogs. Always check the label and consult your veterinarian before offering your pup any new food, treats, or supplements to avoid accidental toxin ingestion.

For more information and tips on your dog’s health, check out the Native Pet blog.