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Cat on grass for article on cats and weed killer

Is weed killer harmful to cats?

While some weed killers (also known as herbicides) are marketed as safe for cats, this really depends on the chemicals used, how the product is applied, and whether safety instructions have been followed.
Cats can be exposed to weed killer by walking on treated grass, brushing against treated plants, or from spray drift.

Ingestion may occur if they groom themselves after contact, eat recently sprayed grass or plants, or drink contaminated water. They can also ingest the product directly if they come across a spillage, or an unsecured container. 

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Symptoms of herbicide poisoning in cats

Cats exposed to toxic weed killers may show various signs of poisoning. The symptoms largely depend on the type of chemicals involved but are likely to include sickness, lethargy, and respiratory problems. The main signs of herbicide poisoning are:

Infographic on herbicide poisoning in cats

Read more: Nine plants that are poisonous to cats

Common weed killer chemicals and their risks

Name of the chemical How it's used Clinical signs
Glyphosate Used in various products for different types of weeds, applied after the weed has begun to grow. Available mainly as a liquid.  While low in toxicity, glyphosate can be very harmful when combined with other chemicals used on lawns and weeds. Signs of poisoning can include vomiting, lower appetite, tiredness, diarrhoea, tremors, severe breathing issues, and kidney problems.
Chlorophenoxy derivatives Frequently found in lawn feed and weed products, available in granular form or as a liquid.

Symptoms include drooling, vomiting, abdominal discomfort, lethargy, ulcers in mouth, possibly bloody stools, lower appetite, progressive weakness, and muscle stiffness.

Benzoic acid herbicides Mainly used for controlling broadleaf weeds in crop fields, orchards and vineyards. Can cause skin irritation and stomach upset. Exposure to large amounts may lead to muscle stiffness, problems with coordination, and shaking, although this is rare.
Dipyridyl (e.g. paraquat, diquat) Used for rapid weed control, effective even in small amounts. Vomiting, abdominal pain and depression appear first. This is followed three to four weeks later by severe respiratory issues and kidney failure, which is often fatal.

Source: Pet Poison Helpline

When should I see my vet?

If you’re worried your cat has been exposed to toxic chemicals in weed killer, contact your vet immediately, particularly if any poisoning symptoms are evident. Be sure to note the name or ingredients of the product, as this information will help your vet determine the most effective treatment. If possible, bring the product container, or a photo of it, to the vet. Quick veterinary care can reduce the severity of symptoms and improve your cat’s chances of recovery.

Diagnosis and treatment for weed killer poisoning

When diagnosing herbicide poisoning, your vet will consider your cat's symptoms and any possible contact with chemicals. They may run some blood tests to check internal organ function. 
In the treatment room, they might start with a decontamination wash to clear the chemicals, give activated charcoal to absorb toxins internally, and provide supportive care like fluids and medication to manage symptoms. They’ll keep a close watch for any complications and in more serious cases, your cat may be hospitalised overnight.

Infographic on herbicide poisoning in cats

Read more: Is weed killer safe for dogs?

How to prevent weed killer poisoning in cats

To prevent your cat from becoming ill from exposure to weed killers, only use pet-safe herbicides and strictly follow the manufacturer’s instructions. When using products, keep cats away from treated areas until the product has dried, or as per manufacturer instructions. Store all gardening chemicals out of reach of pets and clean up any spillages immediately. Consider manual weed removal methods.

Research into weed killer and cats

This letter written by vets and titled Glyphosate toxicity in animals discussed research on treating cats and dogs who had been poisoned by weed killers containing glyphosate. Although glyphosate itself was generally considered low in toxicity, it proved harmful when combined with other chemicals in products.

Cats poisoned by glyphosate often showed signs like vomiting, lack of appetite, and tiredness, but they were less likely to suffer from diarrhoea than dogs. Cats were especially prone to severe breathing problems when exposed to glyphosate, including cases that led to death. Cats faced a higher risk of dying from glyphosate poisoning, with 22% of cases being fatal compared to 5% in dogs. The findings from this study suggested that while glyphosate might not be very toxic by itself, the additional chemicals mixed with it could lead to serious health issues, particularly in cats.

Another study titled Glyphosate-surfactant herbicide poisoning in domestic animals also investigated reports of pet poisonings by glyphosate, collected by the Poison Control Centre of Milan from 2006 to 2012. It found that dogs were poisoned more often than other animals, usually showing stomach upset symptoms like vomiting and diarrhoea. Cats were less frequently poisoned but faced serious issues when affected, with symptoms including vomiting, tremors, and sometimes kidney failure, which could be deadly. Cats had a higher death rate from these poisonings compared to dogs.

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Common questions on weed killer and cats

Can weed killer kill cats?

As the studies above show, if cats are accidentally exposed to high doses or certain chemicals in weed killers, through direct contact or ingestion, it can lead to serious health issues, and in extreme cases, death. That's why it's so important to use these products carefully and follow safety instructions.

What should I do if my cat walks on treated grass?

Wash their paws immediately with soap and water and keep an eye out for any toxicity symptoms showing.

Are natural weed killers safer for cats?

Not necessarily, as they can also contain irritants or toxins that affect cats.

How long after weed killer is it safe for cats?

Even though weed killer labels often suggest that people and pets should avoid treated areas for six to 24 hours, research suggests that chemical residue may remain on surfaces for as long as 48 hours following application. So if you do use products like Roundup, it would be safest to keep pets off treated grass for at least two days.

Need more info about weed killer and cats?

If you’re worried about weed killer poisoning in your cat or any other aspect of your cat’s welfare, have a chat with your local vet.

Find your nearest vet using our find a vet page, or speak to a vet online using our video vets service.

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