Side Effects

The following is a listing of common chemicals found in flea/tick medications and their respective side effects.

  • Imidacloprid – skin irritation. If ingested, may vomit, drool, ataxia, tremors, and lethargy (3).
  • Pyriproxyfen – may cause damage to the reproductive system such as miscarriages, smaller offspring, and birth defects (7).
  • Fipronil – skin irritation. In year long trials, seizures and death (3).
  • Methoprene – skin irritation. If ingested, may vomit, have dilated pupils, changes in breathing and body movements (3). Considered a highly toxic carcinogen, and may cause lesions in the brain, lungs, liver, kidney damage, pulmonary edema, bone marrow ailments and birth defects (7).
  • Novaluron – not an eye and dermal irritant and not a skin sensitizer. No concern for mutagenicity (4).
  • Selamectin – muscle spasms, salivation, neurological signs (6).
  • Permethrin – dermal exposure may cause temporary paresthesia and neurological signs. In cats it may cause hyperexcitability, depression, ataxia, vomiting, anorexia, tremors, convulsions, seizures (3).
  • Amitraz – can reduce hypothalamus function at high doses (5). Sedation, dry skin, low blood pressure, decreased temperature, elevated blood glucose, dilated pupils, slow heart rate, slowed intestinal rate, ataxia, vasoconstriction, vomiting, diarrhea (1).
  • Etofenprox – drowsiness, itching, redness, restless, hair loss. Not an acute eye/skin irritant (Journal 2).
  • Piperonyl Butoxide – dogs exposed at the highest level died, while those at the lowest level had no effects (3)
  • Afoxolaner – no indication of adverse reactions when tested with 16 micro milliliters (Journal 4).
  • Flumethrin – skin lesions that can lead to an excessive absorption through the skin (2).

    A napping dog lying on the couch. Photo by Ava Witter

    A napping dog lying on the couch. Photo by Ava Witter