Permethrin Side Effects in Dogs

The use of permethrin in eradicating a flea or tick infestation can produce side effects in dogs. Symptoms are usually mild and short term, however any neurological side effect should be attended to by a veterinarian.

Permethrin Uses for Dogs

Permethrin is a man-made form of pyrethrin, which is a plant-derived insecticide. Permethrin is used to topically treat or prevent a flea or tick infestation. K9 Adantix, Kiltix and ProTICall all contain permethrin. Both substances interfere with the nervous system of the tick or flea, paralyzing it first before killing it.

Permethrin is safe to use on dogs, as long as it is applied correctly according to the directions. However, this substance is extremely toxic to cats and aquatic animals. It is recommended not to use on dogs that a cat may groom or wait until the application is completely dry. It is also recommended that any dog treated with permethrin does not enter any body of water containing aquatic life for at least 48 hours after treatment.

Permethrin has been FDA-approved for use on dogs and is available over the counter. It must be placed on the skin to be most effective, reaching its highest effectiveness within 3 to 7 days. This product in topical form spreads over the body with the body oils, collecting in the hair follicles. Over time (up to 1 month), the substance is released from the hair follicles onto the hair and skin.

Side Effects of Permethrin

The most common side effect is redness, itching with discoloration, a rash or loss of hair, especially at the application site. If this hypersensitive reaction occurs, it is best to bathe the dog and consult a veterinarian.

More serious side effect include:

  • Vomiting
  • Drooling
  • Diarrhea
  • Increased excitability
  • Lack of coordination
  • Change in body temperature (higher or lower)
  • Seizures
  • Tremors
  • Lethargy

The more serious side effects need faster medical attention.

Other Precautions When Using Permethrin

Sometimes a dog will lick the application site and begin to salivate. This may not be a reaction because permethrin is bitter tasting. It is important that the substance does not come in contact with the mouth or eyes of either the dog or user.

Other precautions include:

  • Do not use with other flea or tick control products that a dog would wear, such as a flea collar.
  • Do not use on debilitated or sick dogs.
  • Do not use on dogs that are exceptionally interactive with cats.
  • Do not use on dogs that regularly play in ponds, unless 48 hours is allowed to elapse after treatment, since the substance is extremely toxic to aquatic life.
  • Consult a veterinarian before using the substance on pregnant or nursing dogs.
  • Consult a veterinarian before using on a dog with liver, heart or kidney disease.

Whenever introducing a new treatment to a dog or any pet, it is wise to observe and or monitor the pet’s reaction to the new substance and the pet’s habits (if there is any change). Adverse reactions to a new treatment are not always immediate. A dog may seem perfectly fine one minute and then in dire shape within a few minutes afterwards.