Side Effects of Fipronil (Frontline) for Dogs

One of the most popular canine flea control products is Frontline for dogs. Fipronil, a chemical insecticide, is the primary active ingredient in the various Frontline products. While promoted as generally safe, it can have some negative effects on a variety of your dog’s systems.

Side Effects and Precautions for Frontline

The only potential side effect listed for Frontline products is skin reactions at the site of application. The skin can become red and irritated, causing itching and promoting your dog to lick or scratch at the site. If irritation lasts for several days you should consult your veterinarian.

In addition to the side effect, there are several precautions that should be followed when treating your dog with Frontline.

Depending upon the Frontline product, it is not recommended for puppies under the age of 10 to 12 weeks. Refer to the product packaging for recommended age restrictions.

Again, depending upon the Frontline product, it is not recommended for aged or debilitated dogs. The spray should not be used on pregnant or lactating females.

The fipronil in Frontline can interact with medications or supplements your dog is currently taking. Be sure to discuss this with your veterinarian to avoid any negative consequences.

Some dogs have a hypersensitivity to fipronil, so it is important to avoid Frontline if your dog is sensitive to these products.

Concerns About Fipronil

While the typical side effect to Frontline is skin reactions, its active ingredient, fipronil, lists other potential concerns when used on canines.

  • Skin problems – As stated earlier, fipronil can cause irritation to your dog’s skin. This irritation can go beyond simple itching as the scratching can cause ulceration and open sores.
  • Nervous system damage – Fipronil is a neurotoxin, causing damage to the fleas’ nervous system. It can have the same effect on your dog, causing symptoms such as convulsions, body twitches, loss of appetite, unsteady gait and other effects.
  • Carcinogen – Fipronil has been shown to cause thyroid cancer in dogs. Because of its carcinogenic qualities, it is important for the person applying the Frontline product to thoroughly wash their hands with soap and warm water to adequately remove the product from their skin.
  • Organ damage – Autopsies have shown an accumulation of fipronil in canine livers and kidneys, causing an increase in organ weight. Fipronil has also been shown to alter the levels of hormone secreted by the thyroid gland.
  • Infertility – Fipronil has also been shown to have an effect on a dog’s fertility. Its use has led to smaller litter size, difficulty in conception, decreased litter weights and increase in litter deaths.

While Frontline products have had successful use in the control of flea populations, there have been negative results seen when dogs have been maintained for extended periods on the products. The fipronil builds up in your dog’s body, giving it the chance to cause problems. If Frontline is your choice for flea control, consider taking a 3 to 6 month break during low flea infestation periods to allow your dog’s body to rid itself of any toxic build up that may have occurred. This will help to avoid the potential of any problems arising from the fipronil.