In 2005, the manufacturer of Frontline Plus, Merial, made a strong statement. The company claimed, in essence, that fleas were becoming resistant to Advantage. Bayer, the company that manufactures Advantage, responded with lawyers a-blazing. In 2006, Merial issued a retraction. It was just one of many episodes in the flea control product wars.

Here is a little history on vets, fleas, and the flea product wars. Veterinarians originally were the equivalent of mechanics. They worked on horses that were used for transportation and other beasts of burden that were used for farming. When the internal combustion engine made vets obsolete in that role, the profession reinvented itself. Although horse and cow vets still exist, most vets these days do what I do. They are doctors for pets.

Fleas have been around for as long as pets have. From the time that vets switched their focus to pets until the time that Frontline and Advantage hit the scene, the main treatment for fleas was a medicine called prednisolone. Prednisolone does not actually treat fleas — it is a steroid that reduces itching and treats skin problems caused by fleas. That’s a sub-optimal way to handle the matter, to say the least.

When Frontline and Advantage were developed, everything changed. The two products worked much, much better and were much less toxic than any previous flea preventative. And they were available only through veterinarians, so vets quickly took to the products not only as effective treatments but also as profit centers for their businesses.

Meanwhile, Merial and Bayer fought like proverbial cats and dogs for market share. The claims and lawsuits of 2005 and 2006 were just part of this battle.

It turned out that vets were mere pawns in big pharma’s game. The companies used vets to bolster the reputations of the products, and then once the products were fully established, they threw vets under the bus and released the products in stores.

Flea preventatives are not profit centers for emergency vets, so I’ve not truly been involved in the fray. But, nonetheless, I have to say something to the folks at Merial at least: Karma is a bitch.

I wish to be clear to Merial and especially to Merial’s lawyers. I am not stating that fleas have become resistant to Frontline Plus. I am not stating that the product generally is less effective than it was.

What I am saying is this: I have seen a lot of Frontline Plus-treated animals who have developed skin problems that I suspect are due to fleas.

Let’s start with my own pal, Buster. For three years in a row he developed skin problems every August and September. I had been using Frontline Plus every month as directed during that time. Three years ago when Buster switched to Comfortis, the problems stopped. He is itch-free and happy as I write this in early September.

And then there was my experience at the vet clinic a few weekends ago. For much of the weekend, I felt like I was working at an emergency dermatology clinic. My first patient of the weekend was a dog who had hair loss, scabbing, and thickened skin on his back at the base of the tail. The symptoms were classic for flea allergy dermatitis, which is a skin condition caused, as the name implies, by allergies to fleas.

I asked the owners about flea control, and they replied that they used Frontline Plus. The pattern repeated itself several times that day. The Bay Area was very warm that weekend, and fleas love heat. I saw at least four Frontline-Plus treated dogs that day for skin problems. In every case, I recommended, among other things, switching flea products.

In fairness, I should point out that none of the dogs in question “had” fleas. Frontline Plus definitely was preventing active infestations from developing. And I remain impressed with the product’s safety margins. However, for allergic dogs, preventing an active infestation is not enough. Severely sensitive dogs can react to just a few flea bites. They need a product that takes no prisoners.

Fortunately, there is a new generation of products that fits the bill. In my experience, Comfortis is the best of the bunch. However, other promising new products include Bravecto and Nexgard (although long-time readers will know of my reservations about any product in which “guard” purposefully is misspelled, and all readers know of my reluctance to pimp any product manufactured, like Nexgard, by Merial).

So is Frontline Plus still working? For now, it still seems to prevent active flea infestations, so it’s probably good enough for dogs who aren’t allergic to fleas. However, if your dog is suffering from skin problems that may in any way be related to fleas (which almost all skin problems are), you may want to consider switching.

Read more from Dr. Barchas:

• Ask a Vet: Why Are Heartworm Preventatives Starting to Fail?
• Ask a Vet: How Many Legs Does a Dog Need?
• Ask a Vet: Will Medical Marijuana for Dogs Become Commonplace?

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!)