Flea and tick medicines have revolutionized dog care.  Veterinarians rarely see flea bite anemia now, for example.  However, too much of a good thing can make your pet sick.  Most flea and tick medicines contain one of two compounds:  pyrethrin and pyrethroid.  Pyrethrins are derived from the Chrysanthemum cinerariaefolium plant, while pyrethroids are synthetic versions of pyrethrins.  Pyrethroids generally last longer than pyrethrins.

When a dog is overdosed with these pesticides or has an adverse reaction to them, it affects the way sodium works in the nerve axons.  This causes repetitive nerve discharges, or twitches and seizures, depending on the dose.  These reactions are more common in small dogs and in young, old, sick, or debilitated animals.

Symptoms vary depending on the type of reaction the dog is having.  Allergic reactions cause hives, congestion, itching, extreme sensitivity, shock, respiratory distress, and rarely, death.

A dog having a reaction from a mild overdose shows excessive salivation, paw flicking, ear twitching, mild depression, vomiting, and diarrhea.

A dog having a reaction from a moderate to severe overdose shows protracted vomiting and diarrhea, depression, incoordination, muscle tremors, and, in some cases, death.

The cause of these symptoms is the excessive application of flea and tick medicine to the dog.  In some cases, such as allergies, any application is too much.  Dogs with abnormally low body temperatures, such as occurs after bathing, anesthesia, or sedation, are predisposed to clinical signs of toxic poisoning.

The diagnosis will be made after a thorough physical exam on your pet, including a history of the pests last few days.  Questions may include: has your pet been exposed to flea and tick medicine, to lawns that have been treated with pyrethrin or pyrethroids, has he been around other animals that have been treated with these substances, and when did symptoms become apparent?

A thorough history of the dog’s movements is the best way to detect pyrethrin and pyrethroid poisoning since it is difficult to detect these forms of pesticides in the dog’s tissues or fluids.

Mild reactions such as salivation, paw flicking, and ear twitching are often self-limiting.  They will wear off in twenty-four to seventy-two hours.  If your dog has been sprayed with the pesticide, wipe with a warm towel and brush the dog dry.  If mild symptoms continue, wash the dog with a mild hand-dishwashing detergent, which will remove the pesticide from your dog.

Moderate to severe symptoms, or symptoms that progress to tremors and incoordination, require immediate emergency care.  Dogs will need to be taken to the veterinarian and hospitalized.  Dogs that are really sick will have to be stabilized, including fluid support and keeping the dog’s temperature normal.  After that, the dog will have to be bathed with liquid hand-dishwashing detergent to remove the pesticide.  Your veterinarian may also prescribe medication to lessen the severity of the symptoms.

Even after treatment, your dog may salivate more than normal for twenty-four to seventy-two hours.

Prevention includes several things.  Proper application of flea control products reduces the chance of an adverse reaction.  Follow the directions on the label to the letter.  For spray products, the correct dose of most sprays is one to two pumps per pound of body weight. Never let your dog go out onto a lawn or other surface that has just been sprayed until the spray has dried.