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Dog Itching After Flea and Tick Treatment? Here Is Why

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The reasons why your dog itches after applying flea and tick treatment are diverse. These include hyperactivity from fleas, dog allergies to antiparasitics, or medical conditions. Contact your veterinarian in case of redness, hair loss, or watery eyes.

Did your dog start scratching more after you applied a flea and tick treatment?

If so, you should know that it is perfectly normal for your dog to itch and scratch harder a day or two after application.

If you notice any other symptoms, you should contact your veterinarian. Your dog may be allergic to the product you used or have other medical conditions that lead to itching and scratching.

In this article, you will find out everything you need to know about why dogs itch after applying flea and tick treatment, how long the itching lasts, if the antiparasitic treatments are toxic to dogs, and more.

Why Is My Dog Still Itching After Flea and Tick Treatment?

Your dog may still itch after applying an antiparasitic product because it is allergic to one of the active ingredients, suffers from other medical conditions, or due to flea hyperactivity in the first 24 hours after application.

It is not pleasant to see your dog still itching after you used antiparasitic products on it. Itching and scratching after applying a product is often not a concern.

Itching after flea and tick treatment can occur due to:

  • Flea hyperactivity in the first 24-48 hours the product takes effect.
  • An allergic reaction to one or more active substances in the product.
  • The dog suffers from other medical conditions that can cause itching.
Dog Still Itching After Flea and Tick Treatment

Flea hyperactivity

Topical antiparasitic products are absorbed in your dog’s skin 24-48 hours after application, releasing the active substance over several weeks.

Fleas coming into contact with the antiparasitics become hyperactive, paralyzed, and then die.[1]

When fleas become hyperactive, they move chaotically on the dog’s fur and skin, causing it to itch even more.

Your dog is allergic to an active ingredient in the product

A sensitive dog typically won’t experience an allergic reaction from the first application of a product. There are rare cases when this can happen though.[2] 

If your dog is allergic, you can notice the following symptoms within 24 hours of application of an antiparasitic:

  • Intensive itching
  • Scratching
  • Redness of the skin, especially in the area where the product was applied
  • Chewing, licking, or biting various areas of the body
  • Sneezing
  • Watery eyes
  • Respiratory problems in severe cases

Related: Flea Bite Pet Allergies

Flea hyperactivity on dogs
Image Source

How Long Will My Dog Scratch After Flea Treatment?

Itching and scratching after flea and tick treatment can last 24-48 hours after application if your dog:

  • Is not allergic
  • Has no skin lesions in the area where you applied the product
  • Suffers from other medical conditions

Contact your veterinarian if your dog is still scratching after 24-48 hours or you notice strange behavior accompanied by other symptoms.

What Other Medical Conditions May Cause My Dog to Scratch?

Other medical conditions that can cause dogs to itch and scratch after flea and tick treatment are skin lesions, dermatitis, sarcoptic mange, flea, food, or seasonal allergies.

If your dog is still scratching after applying an antiparasitic product, and you are sure it is not allergic, your pet may suffer from other conditions:

  • Food allergies
  • Seasonal allergy
  • Flea allergy dermatitis
  • Dermatitis
  • Sarcoptic mange

Seasonal and food allergies are common among dogs. Food allergies are extremely difficult to diagnose because dogs can be allergic to several ingredients at once. 

Both conditions are usually accompanied by other symptoms:

  • Gastrointestinal disorders
  • Lethargy
  • Weight loss
  • Decreased appetite
  • Hair loss
  • Redness of the skin

If your dog suffers from flea allergy dermatitis, it can still scratch after applying the antiparasitic product. The symptoms of this allergy are similar to those of the allergy to antiparasitics.

Sarcoptic mange is caused by mites that burrow into the skin to feed and live. It is accompanied by the following symptoms[3]:

  • Elephant skin (hyperkeratosis)
  • Weight loss
  • Lethargy
  • Dermatitis
  • Alopecia

Dermatitis, whether bacterial or fungal, can cause itching, hair loss, red spots on the skin, rash, and a foul odor.

For any of these medical conditions, talk to your veterinarian for a correct diagnosis and proper treatment.

Related: Ticks on Dogs Symptoms

Medical Conditions May Cause My Dog to Scratch
Image Source

Is Flea and Tick Treatment Toxic to Pets?

Flea and tick treatment are not considered toxic to pets and should not be a cause of concern. These products are usually safe for dogs. Some dogs are more sensitive than others and can develop an allergy after one or two applications. 

Antiparasitic products come in a wide variety:

  • Spot-on pipettes
  • Collars
  • Chewable tablets
  • Sprays
  • Shampoos
  • Powders

If your dog is sensitive, you can use other antiparasitic products instead of those with topical applications, such as chewable tablets.

No matter the product you choose, keep in mind that the dosage or concentration depends on your dog’s weight or age. 

If you apply or administer the wrong concentration you risk intoxicating your pet.

Spot-on pipettes also pose a risk of intoxicating your dog if you are not cautious where you apply them. These products should be applied in the areas where your dog cannot lick the product. This includes areas such as the neck or between the shoulder blades.

If the antiparasitic collar is too loose, your dog can reach it and chew on it, becoming intoxicated.

Signs of Ticks on Dogs
Image Source

If you notice any of these symptoms after you administered antiparasitic products to your dog, contact the vet immediately:

  • Incoordination
  • Tremor
  • Seizures
  • Hypersalivation
  • Difficulty breathing
  • Vomiting
  • Diarrhea
  • Fever or hypothermia
  • Lethargy
  • Loss of appetite
  • Skin rash
  • Scratching

What to Do if My Dog Still Itches After Flea and Tick Treatment?

If your dog is still itching 24-48 hours after administering the antiparasitic product or develops one or more of the mentioned symptoms, contact your veterinarian. They can diagnose your dog and apply the appropriate treatment.

Don’t wait any longer than 48 hours. You risk putting your dog’s life in danger as it can be intoxicated or have other medical conditions.


Antiparasitic products are widely used and recommended by most veterinarians. They are safe for pets and rarely cause allergies in dogs.

If your dog is sensitive and develops an allergy when you apply a particular product, there are many alternatives to choose from.

Make sure you use the right concentration for your dog’s weight and apply the product in the areas where your dog cannot reach.

About Iulia Mihai (DVM)

Dr. Iulia is a certified veterinarian with more than 10 years of experience in the field. With extensive knowledge of diet, care, and medication, she helps Misfit Animals provide readers with accurate knowledge on technical topics.

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