Is Your Flea Control Product Hurting Your Dog?

Many flea preventatives exist. Some work better than others. Some are downright dangerous.


Everybody loves spring, right? The days get longer and warmer. Birdsong fills the air. Trees and plants come to life and bloom . . . and cause hay fever.

People aren’t the only creatures to suffer from springtime allergies. Although they don’t usually get hay fever, dogs also can experience the misery of seasonal allergies. Affected dogs will feel the pain in the spring as the offending plant particles cause itchy feet, armpits, and inguinas (which is a fancy way of saying “groins”). But spring also brings a marked increase in the threat from the most ubiquitous and offensive of canine allergens: fleas.

In the old days vets used to talk about flea season, which roughly correlated to any time of the year that wasn’t winter — we didn’t worry too much about fleas during the colder months. Our understanding of fleas has changed significantly in recent years. In most areas, fleas are a year-round issue. But fleas become much more of a problem in the warmer months of the year.

Although I respect fleas, I certainly don’t like them. They routinely cause itching and hair loss in dogs who are sensitive to the allergens in their saliva. They may trigger skin or ear infections. They spread tapeworms. They can markedly exacerbate a dog’s response to other allergens. Fleas are a leading cause of canine misery worldwide. Thankfully, they are preventable.

Fleas contribute significantly to most of the skin problems suffered by dogs. I therefore recommend regular, year-round flea control in any dog who suffers from any sort of skin problem, even if there is no visible flea infestation. In fact, there is a paradox concerning fleas: Dogs who are highly allergic to fleas will rarely have a visible infestation, but they nonetheless are the dogs who often most benefit from regular, high-quality flea control.

Speaking of high-quality flea control, dog owners need to be aware that some flea products are much better than others. Over the years I have railed repeatedly against the products manufactured by Hartz, Sergeant’s, and BioSpot. The active ingredients in these products usually are pyrethroids — crude, old-school insecticides with low safety margins.

Grave complications can occur if wrong-sized product is applied to a dog, or if a dog product is applied to a cat, or even if these products are applied as directed to an especially sensitive animal. Animals suffering from pyrethroid toxicity may suffer from tremors, disorientation, and seizures, and in my experience toxicity is not uncommon. These products also don’t work well, so they are the worst of all worlds: Toxicity is likely, efficacy is unlikely. I recommend that people stay away from them, but beware: They often bear packaging that is designed to make them look like higher-quality products, such as Advantage or Frontline.

Also, in my experience, natural or herbal flea preventatives are useless and potentially toxic. I have yet to see an herbal or holistic flea remedy that lived up to its claims, but I have seen plenty that had the potential to make pets sick. For instance, some folks still tout garlic as a flea preventative, despite the fact that it doesn’t work and it can cause oxidative damage to blood cells (especially in cats).

In this day and age, it’s almost hard to remember that the stalwarts of flea control, Advantage and Frontline, were revolutionary when they were released. They worked great for years and years, but many people are now questioning their efficacy. The manufacturers of these products become very testy whenever anyone suggests that fleas might be developing resistance to them. However, it is almost inevitable that resistance will develop someday — if it hasn’t already. I don’t have any hard data that show evidence of resistance, but I will say that my pal Buster’s skin problems resolved when I switched him from Frontline to Comfortis (see below).

Advantage and Frontline still work better than many products and they have splendid safety profiles. They are easy to obtain over the counter or from veterinarians. Merial’s patent on fipronil (the active ingredient in Frontline) expired not long ago, and now several companies have begun to make affordable generic versions of Frontline.

In general, if your dog does not have significant skin problems, then Advantage, Frontline, or a generic version of Frontline is probably a good way to go. But beware: K9 Advantix, which looks similar to Advantage, is nowhere near as safe as the original product. And some people who go to the store intending to purchase a generic version of Frontline accidentally walk out with one of the low-quality pyrethroid-containing products.

For dogs with skin problems, or for people who feel that Advantage or Frontline just aren’t doing the trick, there is a newish product that stands out above the rest.

Comfortis is a monthly pill. It causes a small proportion of dogs to vomit, and therefore it isn’t appropriate for every dog. But when it works, it is great. It seems to be as effective as Advantage was once upon a time, and dogs who take Comfortis don’t have greasy necks for two days every month. Comfortis, unlike Advantage and Frontline, is only available by prescription, so switching to it is more complicated than simply running to the store. But most of the people I know whose dogs have tried it, myself included, never look back.

Finally, be aware that there are many other topical products out there for flea treatment. Some, such as Vectra 3D, seem to be quite effective (although Vectra 3D can’t be used in cats, and I always question the safety of a product that is dangerous for cats but supposedly safe for dogs).

Others, such as Revolution, receive mixed reviews. In general I find it’s best to keep things simple. Advantage and Frontline work well for most pets. Comfortis is good for most of the rest.

Editor’s Note: You can get medications for your dog from many sources, but not all of them are trustworthy. Read tis post by Dr. Barchas on the reliability of products bought via online pharmacies. Here are facts about heartworm and how to prevent it; the parasite is transmitted through mosquitoes. The year is still young, and Dr. Barchas recommends several basic things you can do to be a good dog owner in 2013.

Got a question for Dr. Barchas? Ask our vet in the comments below and you might be featured in an upcoming column. (Note that if you have an emergency situation, please see your own vet immediately!)

3 thoughts on “Is Your Flea Control Product Hurting Your Dog?”

  1. My dog developed a fierce licking to all four legs, to the point antibiotics were prescribed along with Apoquel. This started within weeks of the first doses of Brevecto and Interceptor plus. Could one of these be the cause?

    1. My problem is this, I have a dog that is allergic to fleas along with many other things.My dog dermatologist says that I need to give her flea med all year.I have never seen a flea on her or my other dog.But she does have dermatitis.she has ear infections often.she takes 2 doses of serum a day along with a pill for dermatitis and a pill for itching.I cannot stand the thought of having her on this flea meds all year.I have tried Bravetto and
      Nexgard.Heard a lot of bad things about all of them.Is there something
      safe that will really work

      1. I had a pomeranian who was having problems starting 3 to 7 days after we applied Revolution. We did not notice this for years but as our Jack got older the pain hurt him so much he could not hide the pain as well, as animals do not want to show weakness for fear other animals will prey on them. We thought it might be okay with another dog we have now and it seem to be fine at first but now over a few years of applying revolution we see it’s doing the exact same thing to our Josie. Revolution is very toxic to dogs and it’s causing undue pain, seizures and more. Why can we not get medicine for pets tested before they are put out on the market. We are harming and killing our pets with this product and I’m sure there are others like this. I’m having to give my Josie pain medicine until this Revolution wears off. No More Revolution on our dogs ever!!!

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