Borax is toxic to dogs. The toxic dose is 2 to 3 grams per kilogram of body weight, meaning even a moderate amount can poison a small dog. If your dog just ate borax, call your veterinarian or the ASPCA Poison Control Hotline (888-426-4435) immediately. The speed of treatment matters because borax is rapidly absorbed through the digestive tract and can damage the kidneys and central nervous system.
How Borax Harms a Dog’s Body
Borax (sodium borate) is an inorganic compound, which means the body can’t break it down or metabolize it. Once swallowed, it moves quickly from the gut into the bloodstream, where it primarily targets two systems: the kidneys and the brain. The kidneys bear the heaviest burden because they’re responsible for filtering the substance out, and high concentrations can overwhelm and damage them. In the nervous system, borax disrupts normal signaling, which is why neurological symptoms like tremors and seizures appear early.
At the cellular level, boron (the active element in borax) interferes with energy production inside cells. It appears to block key steps in how cells generate fuel, which can lead to tissue damage in organs that depend on constant energy supply. In longer-term exposures studied in dogs, borax also caused testicular damage and reduced blood cell counts, though these effects are less relevant to a one-time accidental ingestion.
Symptoms to Watch For
Symptoms typically appear quickly after a large dose. The first and most common sign is vomiting. Dogs given a significant oral dose of boric acid in research settings vomited shortly after ingestion. Beyond vomiting, the key symptoms of acute borax poisoning include:
- Diarrhea, which may be severe or bloody
- Muscle twitching (fasciculations), visible as rippling movements under the skin
- Seizures, ranging from mild tremors to full convulsions
- Rapid weakness or collapse (prostration)
- Shock or coma in severe cases
If your dog ate a smaller amount, you might only see vomiting and diarrhea. But borax poisoning can escalate. In fatal cases, death may occur within five days of ingestion, so even mild early symptoms deserve a vet call.
Chronic or repeated low-level exposure looks different. Dogs that regularly contact borax dust or residue may develop dry skin, hair loss, and irritation rather than the dramatic neurological signs of acute poisoning.
What to Do Right Away
Your first step is to call a veterinarian or poison control. Have this information ready: the product name and ingredient list, roughly how much your dog ate, when they ate it, and your dog’s approximate weight. This helps the vet assess how serious the situation is and what to recommend next.
Do not try to make your dog vomit unless a veterinarian specifically tells you to. Inducing vomiting is sometimes the right move for certain toxins, but for others it can cause more harm. Cornell University’s veterinary guidance emphasizes that vomiting is sometimes contraindicated, and each poisoning case needs individual assessment. If you can’t reach your regular vet, the ASPCA Poison Control Hotline (888-426-4435) and the Pet Poison Helpline (855-764-7661) are available around the clock.
How Vets Treat Borax Poisoning
There is no specific antidote for borax poisoning. Treatment focuses on removing the toxin and supporting the body while it clears the substance. If the product your dog ate contained more than 10 percent sodium borate, vets may perform gastric lavage, essentially washing out the stomach to prevent further absorption.
The core of treatment is intravenous fluids. These help flush borax through the kidneys more quickly and protect them from concentrating the toxin. Dogs experiencing tremors or seizures receive sedatives or anti-convulsant medications to control the neurological symptoms. Throughout treatment, vets monitor kidney and liver function through blood and urine tests, since these organs face the greatest risk of lasting damage.
Recovery and Outlook
Recovery depends heavily on how much borax your dog consumed relative to their size and how quickly treatment began. A 50-pound dog (about 23 kg) would need to eat roughly 46 to 69 grams of borax to reach the toxic threshold. That’s a few tablespoons, which is a plausible amount if a dog got into a box of laundry booster or a container of ant-killing powder.
Dogs that receive prompt IV fluids and supportive care before kidney damage sets in generally have a better outcome. The critical window is the first few days. Because fatal cases can progress to death within five days, the first 24 to 48 hours of treatment are the most important. Dogs that survive the acute phase without significant kidney or neurological damage typically recover, though your vet will likely want follow-up blood work to confirm the kidneys are functioning normally.
Common Sources of Borax Around the Home
Dogs most often encounter borax through household products that seem harmless sitting on a shelf. Laundry boosters like 20 Mule Team Borax are pure sodium borate. Homemade ant traps often mix borax with sugar or peanut butter, which makes them especially appealing to dogs. Some cleaning products, slime recipes (a real concern if kids leave slime out), and even certain flea treatments contain borax in varying concentrations.
The concentration matters. A product with less than 10 percent sodium borate poses less risk than pure borax powder, though it can still cause gastrointestinal upset. If you use borax-based products for cleaning or pest control, store them exactly as you would any other household chemical: in a sealed container, on a high shelf or behind a latched cabinet door, well out of reach of a curious nose.