• Our pets cannot explain why they react the way they do. Fortunately, we can make educated guesses. When a dog is consistently afraid of flea treatment, it is usually because of an unpleasant sensation related to application.

    Central Nervous System Modulators

    Flea treatments are part of a class of chemicals called central nervous system modulators, which kill fleas by attacking their nervous systems. They have an effect on all nerve cells regardless of species, so your dog may feel a burning or tingling sensation.


    Monthly flea treatments contain organophosphates, some of the most thoroughly researched and powerful pesticides.


    There is growing documentation that monthly flea medications cause nervous system damage in some pets. As these chemicals build up in the body, the effect is cumulative. Pets may also develop allergic reactions to the medication.

    Side Effects

    Side effects of flea medication can include muscle spasms and seizures, as well as vomiting, unconsciousness and tissue damage.

    Early Warnings

    Excessive fear of flea treatment could be an early warning sign that your pet's nervous system is being affected.


    There are a wide variety of plant-based shampoos and sprays that kill fleas on dogs. There are also natural sprays and powders (including diatomaceous earth), which kill fleas on furniture and other surfaces.


    Newman Veterinarian: Flea Fact Sheet

    CDC: Epidemiological Notes and Reports Organophosphate Toxicity Associated With Flea-Dip Products

    Humane Society of the U.S.: Flea and Tick Product Ingredients---What You Should Know

    More Information:

    Facts on Fleas and Treatments

    Flea Treatment Information

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