Is Ortho Weed Killer Toxic to Dogs? Lawn Chemical Risk

Name: Is Ortho Weed Killer Toxic to Dogs? Lawn Chemical Risk
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-03

Is Ortho weed killer toxic to dogs? It depends on the product and the active ingredient. Many common lawn weed killers contain 2,4-D, glyphosate, or dicamba, and these chemicals can cause problems ranging from mild stomach upset to serious illness if a dog eats concentrated product or freshly sprayed grass. The risk goes up with the amount swallowed and how soon after application your dog gets into it.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Most ready-to-use lawn weed killers cause mild signs (vomiting, drooling, diarrhea) if a dog licks a small amount off treated grass, but concentrated product from the bottle is a real poisoning risk.
2,4-D and glyphosate are the two herbicide ingredients most often studied in dogs, and both have been detected in the urine of healthy pet dogs [1][2].
The biggest danger window is the first few hours after spraying, while grass is still wet. Keep dogs off treated lawns until the product has dried completely, and longer if the label says so.
If your dog ate weed killer concentrate, call your veterinarian, the ASPCA Animal Poison Control Center at (888) 426-4435, or Pet Poison Helpline at (855) 764-7661 right away.
Do not make your dog vomit unless a veterinarian tells you to. Some herbicide products contain petroleum distillates or other ingredients that can cause more damage coming back up.

Is Ortho Weed Killer Toxic to Dogs?

Ortho makes many different weed killer products, and the word "Ortho" on the bottle does not tell you how toxic it is. What matters is the active ingredient and its concentration. Some products are ready-to-spray and diluted. Others are concentrates you mix yourself, and those are far more dangerous if a dog chews the bottle or laps up a spill.

The most common active ingredients in American lawn weed killers fall into a few groups:

2,4-D (2,4-dichlorophenoxyacetic acid). This is a synthetic auxin herbicide used to kill broadleaf weeds like dandelions and clover. It is one of the most widely used lawn chemicals in the country. A 2025 study of golden retrievers found detectable urinary 2,4-D in every dog tested, with no difference between dogs with lymphoma and healthy controls at those exposure levels [1]. Another study of pet dogs and cats found 2,4-D among the most frequently detected pesticides in serum [2].

Glyphosate. This is the active ingredient in many non-selective weed killers. It kills most plants it touches. Glyphosate has been classified as a probable human carcinogen, and long-term feeding studies in rats have looked at cancer outcomes from prenatal exposure onward [3]. In dogs, glyphosate exposure is common and usually low-level [1].

Dicamba. This is an aromatic acid herbicide often mixed with 2,4-D in "weed and feed" and broadleaf products. It has a low order of toxicity to domestic animals, and poisoning after normal use has not been reported [4]. It is volatile, meaning it can drift to nearby yards after application [4].

Other ingredients. Many products also contain surfactants, solvents, and petroleum distillates. These can irritate the mouth, throat, and stomach on their own, even when the herbicide itself is low toxicity.

So the honest answer is: some Ortho products are low risk in small exposures, and some are genuinely dangerous. The label is your best guide. Read the active ingredient list and the percentage before you decide how worried to be.

What the Toxic Principle Does in the Body

Herbicides are designed to disrupt plant biology. Most of them do not act on the same pathways in mammals, which is why the majority of organic herbicides cause mainly irritation to the gastrointestinal tract, skin, or mucous membranes instead of organ failure [4].

That said, "low toxicity" is not the same as "no toxicity." Here is what happens with the common ingredients:

2,4-D. In large doses, this herbicide can affect the nervous system and muscles. Dogs are sometimes the more sensitive species in pesticide testing, and dog no-observed-adverse-effect levels were lower than rat levels for many pesticides evaluated by the US Environmental Protection Agency [5]. That does not mean a small lick of treated grass will hurt your dog, but it does mean the margin for error with concentrate is smaller than people assume.

Glyphosate. The main concern with glyphosate products is the surfactant and other ingredients in the formulation, which can cause mouth and stomach irritation. Long-term, high-dose exposure has been studied for cancer risk in laboratory animals [3]. Whether typical pet exposures matter for cancer risk in dogs is not well established in veterinary research.

Dicamba. Low toxicity to pets, with the main risk being stomach upset if a dog eats a lot of treated plant material [4].

Petroleum distillates and solvents. These can cause vomiting, aspiration pneumonia if inhaled during vomiting, and chemical burns to the mouth. This is one reason you should never induce vomiting on your own after a herbicide exposure.

Signs of Lawn Herbicide Poisoning in Dogs

Signs depend on how much your dog swallowed, how concentrated the product was, and how long ago it happened. Mild exposures usually cause gut signs. Large exposures to concentrated product can cause neurologic signs.

Mild to moderate signs

Drooling, lip smacking, or pawing at the mouth
Vomiting, sometimes with visible grass or plant material
Diarrhea
Refusing food or acting mildly subdued
Redness or irritation around the mouth, lips, or paws

Serious signs (seek emergency care)

Repeated vomiting that will not stop
Muscle twitching, tremors, or staggering
Weakness, collapse, or trouble standing
Dilated pupils or unusual eye movements
Difficulty breathing
Seizures
Extreme lethargy or unresponsiveness

Typical timeline

Signs from mouth or stomach irritation usually show up within 30 minutes to a few hours of exposure. Neurologic signs from a large 2,4-D ingestion can appear within a few hours and may worsen over the first day. If your dog licked a small amount of dried, treated grass, signs may never appear at all. If your dog chewed into a concentrate bottle, treat it as an emergency even if your dog seems fine right now, because signs can be delayed.

If you are not sure whether the plant or chemical your dog got into is the problem, our guide to plants poisonous to dogs and what to do when a dog ate a toxic plant can help you sort out next steps.

What to Do Right Now If Your Dog Ate Weed Killer

Stay calm and act in this order.

1. Move your dog away from the source. Close the garage door, pick up the bottle, or bring your dog inside. If the product is on your dog's paws or coat, rinse with lukewarm water and mild dish soap so your dog does not lick more off.

2. Identify the product. Grab the bottle or bag and read the active ingredients and their percentages. Note the EPA registration number if you can. This information changes what treatment your veterinarian recommends.

3. Estimate the exposure. How much was in the bottle before and after? How long was your dog alone with it? Did your dog vomit on its own? Was the grass wet or dry?

4. Call for help. Call your veterinarian, the ASPCA Animal Poison Control Center at (888) 426-4435, or Pet Poison Helpline at (855) 764-7661. Both poison control services charge a consultation fee and can advise you and your veterinarian together.

5. Do not induce vomiting unless a veterinarian tells you to. With herbicide products that contain solvents or petroleum distillates, vomiting can push chemicals into the lungs and cause serious pneumonia. Your veterinarian will decide whether decontamination is safe and how to do it.

6. Do not give food, milk, oil, or home remedies. These can make things worse and can interfere with treatment.

If your dog ate something else and you are trying to decide whether it is a poisoning or a blockage problem, our article on whether a dog that ate a pen needs care walks through that decision.

How Veterinarians Treat Herbicide Exposure

Treatment depends on the product and your dog's signs. Your veterinarian will calculate any medication dose from your dog's weight and health, so no dose is given here.

Decontamination. If your dog just ate concentrate and is stable, your veterinarian may induce vomiting in the clinic with an appropriate medication, then give activated charcoal to bind what is left in the stomach. This is a clinic decision, not a home one.

Bathing. If the product is on the skin or coat, a thorough bath with mild soap removes the source and stops further absorption or grooming.

Supportive care. Most dogs with mild signs get fluids under the skin or into a vein, medication to stop vomiting, and a stomach protectant. This is often all that is needed.

Neurologic care. Dogs with tremors, twitching, or seizures may need anticonvulsants, muscle relaxants, and close monitoring. Some need hospitalization for a day or more.

Blood work. Your veterinarian may run bloodwork to check liver and kidney values, electrolytes, and blood counts, especially after a large exposure.

Monitoring. Mild cases often go home the same day with instructions to watch for worsening signs. Serious cases may stay in the hospital until signs are controlled.

Outlook After Herbicide Poisoning

The outlook is good for most dogs with mild exposures. Drooling and one or two episodes of vomiting usually settle within a day with supportive care.

Dogs with neurologic signs from a large 2,4-D ingestion have a more guarded outlook and need aggressive treatment. Most recover with prompt care, but recovery can take several days.

Dogs that aspirate vomit containing petroleum distillates can develop pneumonia, which is a serious complication. This is the main reason home induction of vomiting is discouraged.

If your dog has underlying heart, liver, or kidney disease, or is very young or very old, the risk from any poisoning is higher. Tell your veterinarian about all medications and health conditions when you call.

How Long to Keep Dogs Off Treated Grass

This is one of the most common questions owners ask, and the answer is on the label.

Wait until the product is completely dry. For most liquid spray products, that means 24 to 48 hours in good drying weather. Cool, humid, or rainy conditions extend that time.

Follow the label's re-entry interval. Some products list a specific number of hours before people and pets can return. That number is the minimum, not a suggestion.

Granular products need watering in. If the label says to water the lawn after applying granules, do that, then keep your dog off until the granules have dissolved and the grass is dry.

Watch for drift and tracking. Herbicides like dicamba can volatilize and move to nearby areas after application [4]. Your dog can also pick up residue on paws and track it inside, then lick it off. Wipe paws after outdoor time during the first few days.

Be extra careful with concentrates. The bottle itself is the highest-risk item in your garage. Store it locked away, never in a low cabinet, and never in a container your dog might mistake for food or a toy.

If your dog has a habit of eating grass, plants, or anything it finds outside, our guide to what to do when a dog eats a mushroom covers a similar decision process for outdoor exposures.

Prevention and Safer Alternatives

You can have a weed-free yard and a safe dog. It takes a little planning.

Read every label before you buy. Look at the active ingredient and percentage. Products with higher concentrations of 2,4-D or glyphosate carry more risk if a dog gets into the bottle.

Spray when your dog is inside. Apply on a dry, calm day, keep your dog indoors during application and until the grass is fully dry, and keep the bottle out of reach the whole time.

Consider non-chemical options. Hand pulling, mulching, mowing tall, overseeding, and corn gluten meal are lower-risk approaches for many common weeds. These take more patience but remove the poisoning question entirely.

Use spot treatment. Treating individual weeds instead of broadcasting herbicide over the whole yard lowers the total amount your dog could contact.

Rinse paws and wipe coats. A quick paw wipe after outdoor time during the first few days after treatment reduces residue your dog can lick off.

Never transfer product to another container. Keep it in the original labeled bottle so you always know what it is in an emergency.

Keep a pet poison number saved in your phone. Having the ASPCA Animal Poison Control Center at (888) 426-4435 or Pet Poison Helpline at (855) 764-7661 already saved saves precious minutes.

Limitations and When to Contact a Veterinarian

This article covers general principles. Your dog's individual case needs a veterinarian who can examine your dog, ask about the exact product, and decide on treatment.

Call the same day if your dog licked wet, treated grass, ate a small amount of granules, or has mild vomiting or drooling that started after outdoor time.

Go to an emergency clinic now if your dog chewed into a concentrate bottle, has tremors, twitching, staggering, seizures, trouble breathing, repeated vomiting, or collapse.

Schedule a routine visit if your dog had a possible low-level exposure days ago and now seems mildly off, has a poor appetite, or has soft stool that will not resolve.

Call poison control first if you are not sure how much your dog swallowed or what the product was. They can help you decide whether to go straight to a clinic.

Do not wait for signs to get worse before calling. With herbicide exposures, early decontamination and supportive care make the biggest difference.

Frequently Asked Questions

Can a dog get sick from licking treated grass?

Yes, but usually only mildly. If the grass is still wet with spray, a dog that licks it may drool, vomit once or twice, or have soft stool. Once the product has dried completely and the label re-entry time has passed, the risk drops a lot. Call your veterinarian if signs last more than a few hours or get worse.

Is 2,4-D worse for dogs than glyphosate?

They cause different problems. Large 2,4-D exposures are more likely to cause neurologic signs like tremors and staggering, while glyphosate products often cause mouth and stomach irritation from the surfactant ingredients. Both are commonly detected in pet dogs at low levels. Your veterinarian will treat based on the product and your dog's signs.

How long after spraying is grass safe for my dog?

Follow the label. For most liquid products, grass is safe once it is completely dry, which is often a day or two. Some labels list a specific re-entry interval for pets. Rain, humidity, and cool temperatures all slow drying and extend the wait.

What if my dog drank from a sprayer or puddle of mixed herbicide?

Treat this as an emergency and call poison control or an emergency clinic right away. Concentrated or freshly mixed product is far more dangerous than dried residue on grass. Do not induce vomiting on your own. Bring the product label with you.

Are "natural" or organic weed killers safe for dogs?

Not automatically. Many organic herbicides still cause stomach or mouth irritation, and some contain essential oils or acids that burn on contact [4]. "Natural" on a label does not mean a dog can eat it. Store all yard chemicals the same way, locked and out of reach.

References

Genotoxic Herbicide Exposures in Golden Retrievers With and Without Multicentric Lymphoma. Veterinary and comparative oncology, 2025.
Exposure profile of four classes of emerging pesticides in pet dog and cat serum from Wuhan, China. Environmental research, 2025.
Carcinogenic effects of long-term exposure from prenatal life to glyphosate and glyphosate-based herbicides in Sprague-Dawley rats. Environmental health : a global access science source, 2025.
Organic Herbicides Toxic to Animals - Toxicology. Merck Veterinary Manual.
Is the 90-day dog study necessary for pesticide toxicity testing?. Critical reviews in toxicology, 2023.