How Long Will My Dog Have Diarrhea After Deworming?

By Josie F. Turner, Journalist specialized in Animal Welfare. Updated: November 13, 2023
How Long Will My Dog Have Diarrhea After Deworming?

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Sometimes diarrhea may occur in dogs after deworming, whether to treat a parasitic infestation or as a preventive dewormer. The causes may be varied and may be related to both the parasites themselves causing the infection and the antiparasitic drug prescribed to prevent or treat the infectious disease. In any case, it is important to pay attention to this clinical sign and notify the veterinarian who prescribed the treatment, especially if it worsens or persists for a long period of time.

If you want to know how long will my dog have diarrhea after deworming, AnimalWised will help. We explain the causes of diarrhea after deworming, the duration of the diarrhea and what treatment options are available.

You may also be interested in: What to Expect After Deworming a Dog

Why do you need to deworm your dog?

To understand the possible reasons for diarrhea in dogs as a result of deworming, it is important to know why the dewormer was given in the first place. Antiparasitic drugs can be administered for two different purposes:

  • Prevention of a parasitic disease
  • Treatment of a parasitic disease

Prevention of parasitic disease

Parasitic diseases must be prevented by two strategies:

  1. Control measures: e.g., do not feed raw food to dogs, provide them with clean and drinkable water, deny them access to rodents, game, dead animals, etc.

  2. Routine deworming: it consists in the regular administration of antiparasitic drugs to prevent the development of parasitic disease.

The frequency with which preventive deworming should be performed depends on several factors, the most important of which are:

  • Epidemiological characteristics of the region: Dogs are at different risk depending on the prevalence of the different parasitic diseases in the geographical area where they live.

  • The individual risks of each dog: The activity your dog performs (hunting dogs, sheepdogs, etc.) and their diet (consumption of raw meat or offal) are particularly important.

Depending on the different factors that determine the risk of each animal, it is necessary to establish an appropriate deworming program. This must always be designed and prescribed by a veterinarian. They will consider the following factors when establishing a deworming schedule for dogs or treating an active parasitical infestation:

  • Dogs that live indoors or have limited access to the outdoors: these are dogs without direct contact to other dogs or access to other risk factors (playgrounds, sandboxes, rodents, prey animals, carrion, snails or raw meat). Dogs with these characteristics are classified as low risk. It is usually sufficient to deworm 1-2 times per year or administer treatment if a parasitical infestation has been diagnosed.

  • Dogs with access to outdoor areas and direct contact with other dogs: these are dogs that have regular contact with other dogs and access to outdoor areas such as parks and public spaces, but do not have access to other risk factors (rodents, prey, carrion, snails or raw meat). Dogs with these characteristics are classified as moderate risk. They should be dewormed 4 times per year or undergo routine testing.

  • Dogs with access to the outdoors, direct contact with other dogs and other risk factors: these are dogs that are used to being in parks and public places. They also have regular contact with other dogs and high-risk animals such as rodents, prey, carrion, snails, etc. Dogs with these characteristics are considered high-risk animals and should be dewormed 4 to 12 times per year.

There are few parasitic diseases that are exclusively related to the age of the animal. The risk of infection exists from birth, so preventive deworming must be performed throughout life. Specifically, deworming should begin at 2-3 weeks of age when they are a puppy and be repeated every two weeks until the animal is 8 weeks old. From then on, deworming should be maintained as often as risk allows, as explained above.

For more details on prevention of parasites in dogs, see this other article on parasites in dogs, prevention and treatment.

How Long Will My Dog Have Diarrhea After Deworming? - Prevention of parasitic disease

Treatment of a parasitic disease

If the preventive measures fail and the animal is affected by parasites, it is necessary to apply a specific antiparasitic treatment against the causative agent of the disease. The specific antiparasitic treatment must be initiated at the time when the parasite species responsible for the infection is determined, and must be repeated depending on the prepatent period of the specific parasite species.

Puppies are particularly susceptible to parasites. Therefore, it is important to treat parasites in puppies as soon as possible, because their health could be at risk. Read this other article on treating parasites in puppies to learn more.

Does dewormer cause diarrhea in dogs?

When a dog has a parasitical infestation, the treatment they use can have different side effects. Deworming medications can sometimes cause diarrhea in dogs as such a side effect. Diarrhea is a common reaction to certain dewormers, although it is often a temporary and mild response. The diarrhea may occur as the dog's body expels the dead or dying worms.

Do preventive dewormers cause diarrhea in dogs?

Preventive dewormers are typically designed to prevent infestations rather than treat existing ones. While these medications are generally considered safe, any medication can potentially cause side effects in some dogs, including preventive dewormers.

Diarrhea can occur as a side effect of preventive dewormers, even if the dog doesn't currently have a parasitic infestation. It's important to note that these instances are also usually mild and temporary.

If a dog experiences persistent or severe diarrhea after taking a preventive dewormer, it's advisable to contact a veterinarian. They can provide guidance on whether the chosen preventive dewormer is the best option for the individual dog and whether any adjustments are necessary. Regular communication with a veterinarian is crucial for maintaining a dog's health and well-being, especially when administering medications.

Causes of diarrhea in dogs after deworming

There are several causes that can explain the occurrence of diarrhea after deworming. Whether it is a preventive dewormer or antiparasitic drug to treat an infestation, a dog may experience the following:

  • The parasitic disease itself: intestinal parasites can cause diarrhea due to their cytotoxic effect and mechanical action on the intestinal mucosa. Even after starting antiparasitic treatment, diarrhea may persist for the first few days while the intestinal mucosa regenerates.

  • Side effects of dewormers: some dewormers may cause diarrhea as a side effect. The susceptibility of the dog to develop diarrhea as a side effect of deworming will depend on various factors, especially the sensitivity of the dog to the product.

  • A dosing error: overdosing on an antiparasitic may increase its side effects, including diarrhea.

  • Improper application: topical dewormers are used for external parasites in dogs and are usually applied in pipette form. They are administered to the space between the dog's shoulder blades to prevent the dog licking and ingesting the dewormer. If the dewormer is applied improperly, the dog may be able to access it and ingest it through licking. Since it is for topical use, ingestion can causes problems such as diarrhea.

Are puppies more susceptible to diarrhea after deworming?

If a puppy experiences diarrhea after the first deworming application, it's not uncommon, and it may be due to various reasons. The deworming medication can lead to the expulsion of parasites from the digestive system, causing temporary irritation and changes in bowel movements. Additionally, some puppies may be more sensitive to the medication, leading to gastrointestinal upset.

How long will my dog have diarrhea after deworming?

The duration of diarrhea in dogs after deworming depends on the reason for which the antiparasitic was administered. If the diarrhea is due to the parasite itself, it may persist for the first few days after the antiparasitic treatment is started.

If the diarrhea is very severe or lasts longer than 7-10 days, be sure to consult a veterinarian, as in these cases the animal may become dehydrated and require fluid therapy. If it is suspected to be a side effect of the medication, it is important to notify the veterinarian who prescribed the treatment. For mild diarrhea, you will likely choose to keep the same medication until treatment is complete. For severe diarrhea, you will need to discontinue the treatment and use a different medication.

To be able to quickly help your dog recover from an upset stomach, keep reading this other article on homemade remedies for diarrhea in dogs.

How Long Will My Dog Have Diarrhea After Deworming? - How long will my dog have diarrhea after deworming?

What to do if my dog has diarrhea due to deworming?

The diarrhea will subside after a few days if the cause is a pathogen. As we have already mentioned, if the diarrhea lasts longer than 7 days, you should consult a veterinarian who will tell you what to do.

If it is a side effect of the medication, the diarrhea should resolve on its own after 24-48 hours. If the diarrhea persists after this time, you will also need to see a veterinarian.

However, you can introduce a soft diet or offer easily digestible food to promote intestinal transit and prevent the dog's condition from worsening. Read this guide to learn more about soft diets for dogs with diarrhea.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to How Long Will My Dog Have Diarrhea After Deworming?, we recommend you visit our De-worming category.

  • European Scientific Counsel Companion Animal Parasites (ESCCAP). (2021). Control of worms in dogs and cats . Guide nº01

  • European Scientific Counsel Companion Animal Parasites (ESCCAP). (2013). Control of intestinal protozoa in dogs and cats. Guide nº06

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