As with all medications, flea products do come with potential side effects.


Dr. Jeanne Haggerty-Arcay

Jeanne Haggerty-Arcay

Seresto collars have been the latest flea preventative to make headlines as an “unsafe” flea medication. But what is the real safety of these medications? Can they be used safely? Or are

they universally harmful to our pets?

Flea medications, like every other medication, have potential risks and benefits. The benefit is that modern flea medications are quite effective at controlling fleas, assuming that the flea population in the environment is controlled. In our temperate climate, we see problems with fleas all year.

Despite common belief, it does not get cold enough here for fleas to simply be a summer issue. We routinely see flea infestations in the winter. Being an “indoor” pet is not enough protection either. Fleas can make their way into our homes from our dog’s trip outside to go to the bathroom, from a trip to the park, on our clothes from visiting a friend’s house, and the list goes on.

Fleas can live on all sorts of warm blooded critters in our yards, in grass and are just waiting for a new host to come along. Once inside our home, they are tough to get rid of and can stay dormant for long periods of time. This means that clearing an infestation can take months or longer.

Flea preventatives are highly effective at controlling flea populations and preventing an infestation, especially when used on a consistent basis on all household pets.

Flea preventatives become critical in controlling allergy dogs. All it takes is a single flea to trigger a cascade of itching, scratching and skin infections in some dogs.

As with all medications, flea products do come with potential side effects. Side effects do vary from product to product and with the type of product. Topical flea products and collars can have topical reactions, such as redness, itching, irritation and hair loss at the site of application or collar. Flea pills can cause stomach upset, loss of appetite, vomiting and diarrhea. Now these side effects can be serious but are generally short-lived and not serious in most pets.

The side effects that have received the most attention are lethargy, seizures and death. These are potential serious side effects for all flea medications, whether it be topical, collar or pill.

Dogs and cats with a history of seizures may be at a higher risk. But even in these dogs the risk is fairly low. Despite the news and social media hype, it is actually uncommon for us to see these serious reactions in pets when the products are used as directed. We most commonly see these reactions in cats using products intended for dogs, in pets receiving a dose too large for their size, or in cases where people have tried to split an individual dose into smaller doses in order to save money. Because the media in recent years has highlighted a few of the flea products, people have started reading labels and noticing these serious side effects. The reality is that these products as well as many drugs (both human and animal) will list these same serious side effects on their labels. We as a society just recently started paying attention to labeling.

So are these products safe? For most pets, the benefits outweigh the risks. But there are definitely pets who have a high risk of developing these serious side effects. With any new medication, the benefits should always outweigh the risks. Don’t rule out flea products based on social media or the latest news. Make an educated decision. Talk to your veterinarian about whether these products are safe for your pet and which specific product might be the best choice. One product may be a better choice than another based on the pet’s health or lifestyle.

Jeanne Haggerty-Arcay