Are Over the Counter Flea Medications Safe for Cats and Dogs?

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Many pets have been made sick or even killed due to use of flea collars or topical flea and tick treatments. Learn why flea and tick medications are dangerous for cats and dogs. Is it okay to use flea medicine on a pregnant cat? Is it okay to use flea

It may come as a surprise to pet owners that some over the counter pet medications, such as used for flea and tick control, are known to be risky, even lethal, to cats and dogs. In fact many cats, dogs, kittens, and puppies, have died as the direct result of their owner CORRECTLY applying a flea collar or other flea control medication.

Many pet deaths have been linked to the use of flea collars, which are losing popularity as they do not do a good job controlling fleas.  There are other flea and tick control products, some of which are spot-on treatments, and are topical (applied to the skin), but some of these topical flea and tick products have also resulted in sick, or even dead, cats and dogs.

The bulk of these pet deaths occurred from the correct use of over-the-counter flea and tick medications and flea collars, sold in pet stores, and department stores.

In fact over a five year period (ending in 2008) at least 1,600 pet deaths were reported to the US EPA related to spot on treatments, read more here.

The US Environmental Protection Agency has done investigations but on the whole the industry is fairly unregulated. All that resulted is the request for labels to be changed, and a few of the more deadly chemicals were banned, however some of the most deadly ones are still present in flea and tick products.  In other words, many flea and tick products are still known to be dangerous and risky to pet health.

Typically pets will start showing symptoms in a very short time following the application, but this is not always the case as some deaths are slow and the result of continued use.


photo source

Common Symptoms of Problems with Toxicity from Flea and Tick Medication

  • Abnormal behavior (hiding)
  • Hyper-excitability
  • Vomiting
  • Convulsions
  • Tremors
  • Lethargy
  • Eye Irritation
  • Excessive Salivation
  • Seizures
  • Itching (easily missed when the pet is already itching from fleas)
  • Twitching
  • Anorexia
  • Chemical burns where the product was applied
  • Death

The Concerns

The concerns from flea and tick medications are two fold, mostly as the chemicals used to kill fleas and ticks are pesticides, they can equally kill other species. As well some pets have allergies to the medications used, causing death in a few hours. In some cases the chemicals were linked to causing brain damage that resulted in the pets no longer knowing when they were hungry or thirsty, as such they would starve themselves to death or die of dehydration.  In other cases chemical burns left the pets with bald patches.

The Chemicals

There are several chemicals responsible for controlling fleas on cats and dogs but the largest group are the pyrethroids. These are used in over-the-counter flea and tick pet medications at a rate of 40% to 80%, which is 8 to 17 times stronger than the most approved for use in humans. You may also want to note that permethrin (a pyrethroid) is listed as Most Toxic and a known carcinogen, in fact wikipedia lists it as highly toxic to cats!

You may be interested to note the label on some products, such as Sergeant's Gold Squeeze-On for Dogs, comes with the warning label “Harmful if swallowed or absorbed through the skin”. Keep in mind this is a product to be directly applied to dogs skin!

Other ingredients that pet owners need to be cautious of are organophosphate insecticides (such as chlorpyrifos, dichlorvos, phosmet, naled, tetrachlorvinphos, diazinon, or malathion) and carbamates (such as carbaryl or propoxur).

Other Points of Interest

Long term use is especially risky as is combined exposure – as when an owner uses both a spot-on topical product and flea collar.

Cats are particularly at risk as they groom themselves are are therefore more likely to ingest the products which makes them all the more deadly. Animals in contact with each other who engage in mutual grooming are at risk (example a mother cat and kittens).

Children who pet treated cats or dogs are at risk of health concerns.



Immediate attention is required as death can be fast. If the pet is wearing a flea collar, remove it.  Pet owners should call their veterinarian at once.   In the United States incidents should also be reported to the EPA at 800-858-7378. If a child has ingested a product the local poison control center should be contacted immediately as brain damage can result.

Pet owners are advised to document any occurrences of problems or death and report them to their nations SPCA, or humane society, as they wish to keep this information on file. Many sites have been set up on the Internet to spread awareness and to offer owners a chance to share their stories.  See HartzVictims for more stories or to share yours.

Other Methods of Flea Control

  • Flea Comb - check for fleas regularly
  • Diatomaceous Earth
  • Control Fleas and Ticks in the area by mowing the lawn, having chickens, ducks, or guinea fowl.
  • Keep the Pet Indoors

Pets should NEVER be treated for fleas or ticks unless fleas or ticks are present.

Other Reading

The Humane Society

Why is My Dog Itching?

Lyme Disease from Ticks

Here is a link to an article about places in the USA you can buy safer pet medications online.

Natural and Safe Ways to Control Fleas and Ticks


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