Dog acting weird after flea medicine

Fleas and ticks are common ectoparasites in dogs. Some medicines are used in dogs to avoid the flea’s proliferation that generates discomfort and even dogs’ health problems. This post will talk about reactions to medications used to protect dogs against fleas and ticks.

Dog acting weird after flea medicine

The dog should not show reactions after the use of flea and tick medications. If the animal shows any symptoms, it may be an indication of dog intoxication, so the animal should be sent to the veterinarian.

The main symptoms of flea drug poisoning are:

  • Dizziness;
  • Animal staggering;
  • Vocalization;
  • Salivation;
  • Vomiting;
  • Loss of appetite;
  • Difficulties in locomotion;
  • Redness and itching of the skin.

Fleas and ticks

These ectoparasites are insects that feed on blood. They reproduce after ingesting blood in animals and several life stages of these insects occur in the environment.

Fleas and ticks can be in all environments from the tutor’s home, such as parks and squares. Many of these ectoparasites can stay in leaves and grass and can climb on dogs when walking and running outside the house.

Fleas and ticks can lead to stress on the animal due to itching and skin lesions. In addition, there are several infectious diseases that can be transmitted by fleas and ticks.

Some dogs may have allergies to flea bites, so it is important to prevent dogs from having contact with this type of ectoparasite.To prevent fleas and ticks, there are currently medications that act as repellents, preventing fleas and ticks from coming into contact with dogs.

Flea medicine

Flea medications can be divided into:

  • Oral medications;
  • Topical medications;
  • Drugs for environmental control.

Oral medications

Oral medications are the least likely to cause reaction in dogs. The drugs were tested and safe for dogs. Thus, flea medicine does not affect the dog, but affects the physiology of the ectoparasites leading to their death. So, for most flea medicines the dogs have no effect or contraindication.

However, some dogs can present allergic reactions and for these animals’ oral medication for fleas and ticks should be avoided.

Topical medications

There are several types of topical medications, including:

  • Spray;
  • Pour on;
  • Repellent collars;
  • Shampoos;
  • Bath solutions.

There are several chemical bases that can be used topically in dogs. They are usually toxic to fleas and ticks leading to the death of these parasites immediately or moments after application of the drug in the dog.

These medicines can already bring harm when ingested by dogs. The reactions are diverse and will depend on the base used by these drugs.

Therefore, care must be taken when using these medications to prevent the dog from licking or eating, it is indicated by the use of cones during the treatment. For baths, sprays and pour on, the use of a cone is recommended until the products dry on the animal’s fur.

Some dogs may also have skin reactions in the region where the medication is applied. A veterinarian should be consulted for better treatment of allergic dogs, avoiding products that can worsen the animal’s health.

Drugs applied at home

Several bases can be used to detect the house, the toxic effect on fleas and ticks can lead to the death of these ectoparasites, in addition to eliminating eggs and other larval stages present in the environment.

In general, strong insecticides are used that can intoxicate the dogs, and therefore, at the time of detection, it is important to remove the animal from the environment. Some drugs will stay active longer in the environment and during this period the dog should not have contact with the place.

How to proceed when the dog has reactions to flea medicine

If the animal shows any symptoms, it should be taken to the veterinarian. At the veterinary hospital some laboratory tests can be done to assess the dog’s health status.

When intoxication is identified, the dogs must be hospitalized for observation. Dogs receive fluid therapy to help eliminate toxic metabolites and vitamin supplements to replenish nutrients and protect liver and kidney function.

Dogs have discharge when they show clinical improvement, without any apparent symptoms and with laboratory tests within the reference values for the species.

When dogs are not treated properly, many of them can have serious reactions that affect the liver, kidney, and nervous system irreversibly. So many dogs die.


Some flea medications are very safe for use in dogs, as is the case with oral medications. On the other hand, some animals may show some type of reaction, so it is important to consult with the veterinarian. In addition, the use of topical and environmental detection medications present a greater risk of intoxication by dogs, requiring additional care. Whenever the animal presents any symptoms of intoxication, a veterinarian should be consulted.

Frequently Asked Questions (FAQs): Dog acting weird after flea medicine

Why does the dog change behavior?

Several factors may be linked to changes in behavior in dogs, including age, health and changes in the environment.

How to know if the dog is in pain?

Dogs can show pain by several signs such as:

  • Apathy and isolation;
  • Lack of appetite;
  • Vocalization;
  • Shrunk back;
  • Lameness;
  • Walking resistance;
  • Aggression.

How to get rid of fleas on a dog?

Medication for fleas can be used in dogs, which can be oral or topical. Dogs should bathe with warm water and dog-specific shampoos. The environment in which the animal lives must be detected and cleaned to avoid the proliferation of other phases.


Coppinger, R., & Coppinger, L. (2001). Dogs: A startling new understanding of canine origin, behavior & evolution. Simon and Schuster.  

Medeiros, R. J., Monteiro, F. D. O., Silva, G. C. D., & Nascimento Júnior, A. (2009). Casos de intoxicações exógenas em cães e gatos atendidos na Faculdade de Veterinária da Universidade Federal Fluminense durante o período de 2002 a 2008. Ciência Rural, 39, 2105-2110.

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