Side Effects in Dogs From Using Frontline

Frontline is a brand of flea medication for dogs that is applied topically. This medication can be purchased from a veterinarian, at a pet store or through an online pet pharmacy. According to 1-800-PetMeds, Frontline kills adult fleas, flea eggs and larvae. The active ingredients are fipronil, an insecticide, and S-Methoprene, which kills the eggs and larvae. Dogs can experience certain side effects from Frontline, so be aware of them if it's the first time you're using the flea repellent on your dog.

  1. Irritation

    • Frontline is applied between a dog's shoulder blades so the dog can't lick off the medication. This area can become irritated after using Frontline. Skin irritation can cause the dog to scratch at the area. The skin can become red and dry. This symptom shouldn't cause worry unless it persists for more than a couple of days. If it does continue to be a problem, speak to a veterinarian about a different flea repellent.

    Interaction With Other Medications

    • There are possible interactions between Frontline and other medications. A veterinarian should be consulted if the dog is on other medications. These side effects can adversely affect a dog's skin or coat, since Frontline is not absorbed internally, but is spread through the hair follicles.

    Oily Fur

    • The dog's coat can appear oily at the point of application for a couple of days. According to Frontline's website, the medication collects in the pet's natural skin oils so it spreads over the body. Because the medication is collected, and not absorbed, the area can appear wet and feel oily for a couple of days.