Topical treatments are available over-the-counter and by prescription to combat flea infestation. Once the topical solution is applied to the coat of the cat or dog, the active ingredients work to kill fleas. The insecticides found in topical flea products may cause side effects in your animal, including skin problems. Topical flea products should not be used on ill or pregnant animals without the approval of a vet.
Itching
According to the Daily Puppy website, the most common side effect reported in the use of the Advantage brand topical flea treatment was itching. Out of the dogs tested with the product, 14.8 percent experienced itching after application. As the fleas begin to die, there may be a temporary increase in the frequency of the animal scratching. If the scratching continues, it may be a reaction to the flea treatment product or a recurrence of the flea infestation.
Irritation
Fipronil is a common ingredient found in topical flea treatment products, such as Frontline and Top Spot. The fipronil needs to be applied directly to the skin of the animal in order to prove effective at killing fleas. Side effects reported by Newman Veterinary include skin irritation. Irritation and hypersensitivity occurred directly at the application site.
Hair Loss
Fipronil also has been reported for causing nervous system damage and reproductive damage, according to the Animal Protection of New Mexico website. In addition to these issues, multiple skin problems were reported by the organization. This included hair loss not only at the application site of the topical flea product, but the surrounding areas as well.
Ulcerations
Ulcerations, skin sloughing and chemical burns were other adverse effects of the skin reported by the Animal Protection of New Mexico website when using products that contain fipronil. Products that contain methoprene, ethanol and permethrin had other side effects associated with them, but no skin problems reported.
