Is weed killer safe for dogs?
First Published: 05/06/2019
Last Updated: 11/10/2024
Most over-the-counter weed killers, also known as herbicides, are usually safe for dogs if used correctly and allowed to dry completely on the treated areas. However, exposure to certain chemicals in weed killers, particularly when wet, can lead to health issues in dogs, ranging from mild stomach upsets to severe poisoning.
Always read the weed killer label carefully and follow application guidelines to ensure your dog's safety. You should also prevent your dog from accessing treated areas until they're dry, and seek immediate vet care if your dog does come into contact with any chemical product.
Which chemicals should dog owners avoid?
Problems usually occur when dogs are exposed to weed killer that hasn’t been given enough time to dry, or because herbicides haven't been used or disposed of properly. Dogs that swallow or lick herbicides can become ill, and some effects might take a long time to show. The table below lists some common herbicides and their dangers to dogs.
Common weed killer chemicals and their risks
| Chemical | Risks |
|---|---|
| Glyphosate | Widely used in agriculture and gardens. Generally low in toxicity, but can cause vomiting, diarrhoea, tremors, and breathing issues when mixed with other chemicals. |
| Phenoxyacetic compounds (e.g., 2,4-D) | Common in lawn care. Safe if dry, but large doses can lead to weakness, respiratory problems, and nervous system issues. |
| Chlorophenoxy herbicides | Found in lawn products. Symptoms include drooling, vomiting, lethargy, ulcers, bloody stools, and muscle stiffness. |
| Benzoic acid herbicides | Used in crop fields and orchards. May cause skin irritation, stomach upset, muscle stiffness, and coordination issues. |
| Pyridine, dinitroaniline, benzamizole | Low toxicity. Rarely causes stomach upset and discomfort. |
| Dipyridyl herbicides (e.g., paraquat, diquat) | For rapid weed control. Early signs include vomiting and depression, followed by severe respiratory issues and kidney failure. |
Sources: Pet Poison Helpline and Merck Veterinary Manual
Symptoms of weed killer poisoning in dogs
Symptoms such as difficulty breathing, convulsions, and stomach upsets can occur following exposure to some herbicides. It's important to remember that these symptoms can be caused by other issues too. However, if your dog became sick soon after you applied weed killer to your lawn, and they were fine before that, the weed killer might be the reason. These are the most common symptoms of herbicide poisoning in dogs:
- Vomiting or diarrhoea
- Strained or laboured breathing
- Restlessness or abnormal behaviour
- Fits or seizures
- Muscle tremors
- Excessive drooling
- Reduced appetite
- Abdominal (tummy) discomfort
Read more: How to help a constipated dog
What to do if you're concerned about herbicide poisoning?
If you’re worried about your dog’s exposure to herbicides, contact your vet immediately. It’s recommended to bring the chemical bottle with you, or take a picture, so the vet can look closer at its ingredients. It’s also helpful if you know how much contaminated grass your dog has eaten and when they ate it - did they have a brief nibble, or did they not stop eating grass until you told them to stop? If your dog has had access to the actual weed killer product (i.e. licked up a spill or got at the bottle), rather than just contaminated grass, seek veterinary advice urgently. As always, prevention is better than cure. When using any weed-killing agents, make sure you carefully follow the instructions on the bottle. As you apply the chemical, keep your dog somewhere contained and safe — preferably indoors — and give the treated area a chance to dry before letting your dog near it.
Can weed killer kill dogs?
While uncommon for most over-the-counter weed killers, some can be fatal if your dog swallows a large amount, e.g., if they drink it from the bottle following a spillage. To be extra safe, always store weed killers and other chemical-based household products securely, out of your dog’s reach. If you spill chemicals, clean up the mess immediately and keep your dog away from the affected area until it dries.
Read more: Safety tips for keeping your pet safe
Treatment for herbicide poisoning
The severity of weed killer poisoning in dogs depends on the amount of herbicide or contaminated grass swallowed. Treatments can vary and may include the administration of activated charcoal or other absorbents, as well as supportive care such as fluids and medication to manage symptoms. It's important to be cautious and to contact your vet if you notice any of the symptoms listed above.
Research into herbicide poisoning in dogs
The study detection of herbicides in the urine of pet dogs investigated the presence of herbicides in dogs' urine after exposure to treated lawns, revealing widespread contamination even on untreated lawns. This is due to something called chemical drift. Findings indicated that herbicides can linger on grass for over 48 hours, and even longer in certain weather conditions. The research suggested a need for further study to evaluate the risks of herbicide exposure in both humans and pets.
Another study, entitled canine exposure to herbicide-treated lawns, investigated the absorption of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) by dogs on treated lawns. Findings revealed that dogs exposed to lawns treated with 2,4-D had significant levels of the herbicide in their urine, especially within two days of application. The risk of exposure decreased over time but remained detectable for up to a week. Given 2,4-D's potential link to cancer, such as lymphoma in dogs, pet owners are advised to keep their pets off recently treated lawns and to monitor their health for any signs of herbicide poisoning.
Another research paper on paraquat intoxication studied the cases of dogs who had been exposed to paraquat, which is also a toxic herbicide. When ingested, inhaled, or absorbed through the skin, paraquat caused severe respiratory and gastrointestinal symptoms, progressing to significant lung damage and systemic failure. Despite treatments aimed at reducing absorption and managing symptoms, all affected dogs were put to sleep due to the poor prognosis. The study highlighted the urgent need for effective treatments and raised awareness of the high risks associated with paraquat.
Need more info?
There are many ways to protect both your garden and your dog! For more information on weed killer poisoning, or any other aspect of your dog’s health, speak to your vet.
Find your nearest vet using our find a vet page, or speak to a vet online using online video vets.