Is Frontline Safe for Dogs?

An expert walks you through the potential dangers of Frontline and Frontline Plus for dogs

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Fleas and ticks can be pesky problems for both dogs and their owners not to mention that certain ticks can spread Lyme disease. Luckily, there are many flea and tick preventatives available, including over-the-counter and prescription options. One of the most commonly used preventatives for dogs is Frontline. While this product is widely available, easy to use, and generally effective for controlling ticks and flea infestations, Frontline is not without safety concerns — no medication is.


Frontline, a flea preventative, can have adverse side effects for both pets and humans.
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As a pet parent, it is important to be knowledgeable about the appropriate use and possible side effects of any meds you give your dog. This way, you'll know what to look for, and you'll be able catch problems early. Speak with your veterinarian about the best flea and tick preventatives for your dog.


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What is Frontline Plus for dogs?

Frontline is a popular over-the-counter tick and flea treatment and preventative marketed for use in dogs‌. (There is also a feline Frontline formula.) The medication comes in a liquid that is applied to the dog's skin between the shoulder blades. The primary chemical in Frontline is fipronil, which disrupts insect neural receptors. Frontline Plus kills fleas and ticks, chewing lice, and certain mites.


Is Frontline safe for dogs?

Frontline is generally safe for dogs when used properly.‌ However, there has been some controversy over the safety of its chemical ingredients, with some pet owners claiming their dogs have experienced adverse reactions. While Frontline is approved for pesticide use on dogs by the United States Environmental Protection Agency (EPA), some canines do experience allergic reactions and side effects, including inflammation and hair loss at the site of application. Frontline is not safe for ingestion, and it can have very serious side effects, including death in extreme cases, if your dog eats it.


Active ingredients in Frontline Plus

Frontline uses two active ingredients to kill insects:

  • Fipronil:‌ Fipronil is a chemical that disrupts insect neural receptors. Fipronil is a known carcinogen whose potency increases in sunlight.
  • S-Methoprene:‌ S-Methoprene prevents insect exoskeletons from developing, halting insect growth. According to the EPA, S-Methoprene has a low toxicity potential for animals and humans.


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Side effects of Frontline Plus for dogs

The incidence of documented side effects from Frontline is low, with itching, hair loss, and redness usually localized to the area of application. Side effects include:



  • Itching
  • Redness
  • Hair loss
  • Drooling
  • Diarrhea
  • Vomiting
  • Seizures

The latter four side effects have been noted mainly when a dog ingests Frontline.

If your pet is experiencing any of the above after a topical flea preventative is applied, contact your veterinarian. In the case of extreme gastrointestinal upset or seizures, take your dog to your veterinarian or emergency animal hospital immediately.


Frontline side effects for humans

While Methoprene-S can cause skin irritation and eye irritation in humans, Fipronil is a suspected human carcinogen and endocrine disruptor. Fipronil can also be toxic to the nervous system, particularly if ingested. Signs of a negative reaction include:


  • Headache
  • Dizziness
  • Nausea/vomiting
  • Weakness
  • Seizures

Frontline can also cause extreme ocular irritation if it makes contact with the eyes. Children are particularly susceptible to all Frontline side effects because they are more likely to pet the dog and put their hands in their mouth or touch their eyes, play with dog toys, or play in dog areas. Contact Poison Control at 1-800-222-1222 in the U.S. if you suspect a human has ingested Frontline.

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How to avoid side effects when using Frontline Plus

Follow all safety precautions labeled for Frontline. Carefully apply it topically and only between the shoulder blades of your dog. Using this application site should prevent your dog from being able to lick off the product.


Dogs should never be allowed to ingest Frontline. Use an Elizabethan collar to prevent licking while the product dries if necessary. Other pets might want to lick Frontline off your dog, so monitor them closely to stop this from happening. If the preventative is ingested by any pet, consult your veterinarian immediately.

For your own protection, you can wear gloves when applying Frontline and then wash your hands thoroughly afterward. Keep the product out of the reach of children and pets.

Alternative flea and tick treatments for dogs

While Frontline has been a successful treatment without problems in many dogs, some pet owners who are reluctant to use it on their dogs have found anecdotal success with home remedies, like certain essential oils. You can reduce the likelihood of your dog getting fleas by bathing the pet frequently and thoroughly cleaning their environment on a regular basis. Keep in mind, however, that alternative treatments will not be effective for controlling all stages of the flea life cycle. For example, bathing your dog with soapy water will kill adult fleas that are currently on the dog, but it will not eradicate the flea larvae, flea eggs, and pupae that persist in the environment.

Beyond Frontline, there are many other dog flea and tick preventatives on the market that target all life stages. Talk it over with your veterinarian to see which products might be best for flea control and tick protection on your dog.

The bottom line

Fleas and ticks are a common issue for dogs, and topical products, like Frontline, are aimed at helping pet owners get rid of them safely and efficiently. While Frontline, which contains active ingredients Fipronil and S-Methoprene, is generally safe for dogs, it can cause side effects. Skin irritation might occur at the application site, and some dogs can be allergic to the product. The preventative is also toxic if ingested, so contact your veterinarian right away if your dog licks Frontline or any other topical flea and tick control product. Read the insert that comes with the preventative and follow all the safety precautions to protect yourself and your pet.