Can Worms Cause Hair Loss In Dogs?

This dog has a very thin coat in places. But can
such a loss be caused by worms?

Have you just noticed that your dog is losing hair after having recently been treated for an infestation of worms of one sort or another?

Although it is not impossible, it is incredibly unlikely that this hair loss is due to worms. 

And let me start by explaining why…

Top Treatments Worms

Even if your dog has an infestation of worms, it should not on its own cause hair loss.

Worms can be the source of considerable distress for a dog and their owner but they are not thought to cause hair loss.

However, worms are commonly treated with a range of medicines and so I thought I would investigate whether any of those medications have any known side effects that include hair loss. 

I have just quickly looked at a list of the most popular medications used for worming in dogs. 

And they are:






All of these medications have been used successfully for years in veterinary practice and they are all considered very safe.

But any medication has the potential for side effects and so I dug a little deeper to find out some more of the side effects of each of these drugs. 

And out of all of them, the only medication that is known to have a side effect that might cause hair loss in dogs is fenbendazole.

Among its known side effects, itchiness and hives are mentioned which could lead to hair loss in a dog. But to repeat, it is very, very rare for this drug to cause any side effects.

None of the other listed drugs have any known side effects that might cause hair loss in dogs. The side effects included things such as seizures, muscle spasms and excessive drooling but nothing that would directly cause hair loss. 

Moxidectin is an interesting case. Recognised side effects for dogs include panting and muscle tremors but a known side effect when it is used with cats does include scratching and excessive grooming. 

What do we mean by worms?

Did you know that there are 6 types of worms commonly found in dogs? No, I wasn’t aware that there were that many different types either…

And just the thought of these things are plain disgusting







To go through some of the main points about these worms.

Many of these worms can be passed from dogs to humans, which is why we must all take prevention very seriously. 

All but two of these worms live in a dog’s intestine. Heartworms, which live in a dog’s heart and lung worms which breed in the dog’s lungs. 

The most common worms are roundworms, which many puppies are born with roundworms because they are passed from their mother. 

Dogs can become infested with many of these worms by eating wild animals such as rabbits or birds, dead or alive) that become infested with them.

Hookworms can be fatal to puppies because of the amount of blood that they consume. 

Overall heartworms are the most dangerous type of worm, which is not surprising when they live in a dog’s heart.

These worms are transmitted by mosquitoes and cases are higher in areas where mosquitoes are most prevalent, such as the Atlantic and Gulf coasts of the U.S. 

Six common symptoms of worms in dogs?

There are two difficulties when looking at the symptoms of worms in dogs.

Firstly, many of the symptoms are not just specific to an infestation of worms. For instance weight loss. If your dog is suffering from weight loss then it could be suffering from any number of diseases not just worms.

Secondly, the best symptom is to physically see worms in a dog’s faeces, vomit or on their bottom.

But, get this- your dog might have worms but you won’t necessarily see them. 

Tapeworms look like little grains of rice in your dog’s stool but it is unlikely that you will be able to physically see  any other type of worm because they can only be identified by a stool sample being examined by a microscope.

But, with all that said and done, here are the six most important symptoms that could indicate that your dog has worms.

[1] Worms in dog’s faeces or on dog’s bottom

[2] Diarrhoea and vomiting

[3] Weight loss

[4] Swollen stomach

[5] Lethargy

[6] Abdominal pain

[1] As we have already said, this is your best symptom because if you see worms, the dog definitely has worms.

[2], [3], [4], [5] are all physically obvious symptoms- you know when each of them is happening just by looking. What you don’t know is whether combined or on their own they indicate that your dog has worms.

[6] is a harder one to spot. It might be easy to identify that your dog is in pain but much harder to say for certainty that the pain is coming from the abdomen. 

How do dogs get worms?

There are five main ways that dogs can get worms.

*eating infected stool

It is time to be grossed out again. 

A study in 2012 showed that 16% of dogs or one in six of them ate stool regularly and 25% or one in four of them ate stool at least once. 

The same study showed that females are more likely to eat it than males and on nine out of ten occasions, dogs ate fresh stool (which was less than two days old over stool that was “older”.)  

*eating, touching or ingesting infected soil

This is slightly easier to read and it is all to do with the fact that a patch of ground that has had worms on or infected fleas (via stool etc) can stay infected for months. Dogs are at risk even if they walk on the soil and then later ingest tiny particles of it as they are cleaning themselves. 

* eating infected grass

Dogs eat grass. Sometimes they might eat it because it has water on it and they are looking for a drink or because they are trying to make themselves vomit or even to balance their diet with a bit of vegetation or fibre.

*having fleas and ingesting them whilst grooming

This is a bit scary and one that I didn’t realise until I did a bit of research.

If a dog has fleas then when they are grooming themselves they might accidentally eat a flea. 

Quite a weird thought until you look more closely at how a dog grooms themselves- they almost seem to chew on their skin with their front teeth, don’t they? 

And then you think, yeah that’s not so far fetched after all. 

Now, if those fleas are infected with a worm then the dog is at risk of developing worms.

Which is why regular flea treatment is so important

*eating (dead or alive) wild animals that have been infected with a type of worm. Think rats, rabbits or birds.  

Another unsavoury option!

How many dogs are guilty of this?

I know that my sister in law is struggling with this very thing right now. 

She has a 4 month old Golden Retriever who likes nothing more than to disappear into the hedgerows and to come home with a dead rat or pheasant in its mouth…Yum, yum.

I would have thought the biggest risk of this was an upset tummy but now I think that it could be the threat of worms..

Combined, doesn’t that list make you never want to let your dog outside again?! 

It is a bit all encompassing and scary. 

8 common causes of hair loss in dogs

I think that we are now at the stage where it is unlikely that an infestation of worms are causing hair loss in your dog.

So what is?

Here are eight of the most common causes of hair loss in dogs

[1] Infestation of parasites- mites, fleas or lice

[2] Over grooming- parasite or anxiety

[3] Skin conditions- eczema or dandruff or hot spots

[4] Nutritional deficiencies

[5] Food allergies

[6] Complex conditions- Cushings disease and cancer tumours

[7] Scars or wounds

[8] Inherited conditions

Top treatments for hair loss

Since there is a wide range of causes of hair loss in dogs, so is there a very wide range of treatments.

But here are some of the most common and best treatments

[Antibiotics, antifungals and steroids- to treat infections and inflammations

Antihistamines- for allergic reactions

Medicated shampoos (with hydrocortisone) 

Flea and tick medication

Elizabethan collar- for overgrooming

Natural/ holistic treatments

If you want to go down a more holistic route, then I have a few solutions for you to try. They include using a humidifier, trying apple cider vinegar or lemon juice

Top breeds for hair loss

Closing Thoughts

So, it looks as though the cause of your dog’s hair loss will almost certainly not be from worms. 

There is a very, very slim chance that as a result of a medication used to treat your dogs for worms it might cause hair loss- but the chances of that are very small. 

What is more likely is that your dog’s hair loss is caused by other non worm factors, many of which I have discussed in this article. 

Photo Credits

 ¹ Photo by Teresa Trimm on Flickr