Itchy dogs

 

Itchy puppyItchy dogs are a big problem in our practice. Recent reports suggest that up to 40% of non-routine veterinary patient visits are skin related, usually with scratching and irritation of the skin.  

 

This page has been written to supplement a vet visit by giving information and background that can’t possibly be given in one consultation.  It has also been written to try and present some evidence based therapies for itchy dogs that have been proven to be beneficial in large scale studies so that owners are not tempted to try product ‘abc oil’ from farmers market ‘xyz’ even though John from the market said it worked for his dog.

 

We know that the ‘lets give this a try’ approach breeds confusion and frustration amongst owners and ends up with dogs not being treated properly because owners have ‘tried everything and nothing works!’.  

 

This page will help owners to:

 

  • understand what is happening in their dogs to make them itchy

 

  • give owners some tools for being able to alleviate symptoms as much as possible

 

  • allow owners to understand when they can be helping their dogs at home and when they need to call the vet for assistance

 

  • enable owners to visualise a path towards diagnosis of their dog’s skin condition

 

  • help owners to understand that most conditions that cause scratching are manageable but not curable

 

First, some definitions:

 

Itch(Pruritus)

An uncomfortable sensation that generates the desire to scratch.  Scratching in dog’s may include rubbing, chewing, biting and licking.

Allergy

Allergy occurs when a dog’s immune system reacts to substances in the environment that are usually harmless to most dogs.

Atopic dermatitis

A genetically determined skin problem that results in inflammation and itching of the skin in specific areas that is associated with antibodies to environmental allergens.

Food allergy

An allergic condition of the skin that resolves once a hypoallergenic diet is exclusively fed.

Flea allergy

An allergic condition of the skin (usually above the base of the tail) that resolves once fleas are eliminated from the dog’s environment.


 

Why do dog’s scratch?

 

Itchy pupThe simple answer is because they are itchy!

 

The complex answer is that itching is caused by an intricate interaction between inflammatory cells and the molecules they release whenever they are activated by the immune system.

Scratching is a physiological response that gives short term relief from itching by causing pain that then reduces the sensation of itch.

 

It puts our dogs’ scratching in a different light if we think of it in terms of them willing to make themselves hurt just to alleviate the uncomfortable sensation of itch.

 

How much itching is too much itching?

 

It can be difficult as a dog owner to know when your dog is itching more than it should be.  In general terms, if a dog scratches enough to cause redness of the skin or hair loss that can’t be controlled by home treatments, then the dog should be seen by a vet.  The following table also helps to define the level of itch that a dog is suffering from - any grade over 2 will need to be seen by a vet.

 

Canine itch scale (Itch includes scratching, biting/chewing, licking or rubbing)

 

Grade 0

Normal dog: There is minimal itching. There is no more itching than before the disease began.

Grade 1

Very mild itching: There are occasional episodes of itching. There has been a small increase in itching compared with before the disease began.

Grade 2

Mild itching: More frequent episodes of itching but itching stops when dog is sleeping, eating, playing or otherwise distracted

Grade 3

Moderate itching: Regular episodes of itching are seen when the dog is awake.  The dog occasionally wakes up because of itching but the itching stops when the dog is eating, playing, exercising or otherwise distracted.

Grade 4

Severe itching: Prolonged episodes of itching are seen when the dog is awake. The dog regularly wakes up because of itching or itches in its sleep. The itching can also be seen when the dog is eating, playing, exercising or otherwise distracted.

Grade 5

Extremely severe itching: Almost continuous itching which does not stop when the dog is distracted, even in the consulting room.  The dog needs to be physically restrained from itching.

 

How is a vet going to help my itchy dog?

 

There are three aspects to the treatment that your vet will give.  


 

Your vet will give some treatment to control the immediate discomfort that your dog is in.  Most dogs are presented to vets for flares of their skin condition due to a phenomenon called the itch-scratch cycle - the act of licking, chewing, biting or scratching damages the skin and causes MORE itch. The dog will often require some infection control as well because infection with yeasts or bacteria is an important complicating factor in dogs with itchy skin problems.

 

If this is not the first episode of skin problems that your dog has had, your vet will talk about home treatments that should help to keep your dog comfortable and reduce the frequency and severity of flares in the future.  These treatments will be mentioned later but it is most important that these treatments are performed when your dog’s skin is looking good as most home treatments will not be able to control a flare once it has spiralled out of control.

 

If your dog has had more than a few episodes of skin problems or the itch is quite severe, your vet will discuss some diagnostics to try and narrow down the cause of your dog’s itching.

 

What types of conditions make our dogs itchy?

 

The common causes of itch in dogs mainly boil down to parasitic, infectious or allergic skin disease.  The most common causes of itchy skin in dogs are mentioned below.  Obviously there are more causes but there is a truism in veterinary medicine that “common things occur commonly” and this is very true in dermatology.  As long as we stick to a logical diagnostic process, most skin problems will be sorted out.  If things turn out a bit unusual then there is always the option to refer to a specialist dermatologist.

 

Common causes of itch in dogs:

 

Parasites

Sarcoptes mites

Demodex mites

other mites (much less common)

Infections

bacterial infection

yeast infection

Allergic skin disease

Atopic dermatitis

Food allergy

Flea allergy

Contact allergy

 

So what itchy skin condition does my dog have then?

 

Itchy skin conditions in dogs are generally diagnosed by a series of rule outs.  It is impossible to diagnose what skin condition your dog has on his/her first visit.  We need to rule out conditions one-by-one and assess response to certain medications along the way to coming up with a definitive diagnosis.  This can be frustrating for owners but there is not one test that we can do to eliminate all possibilities in one go.  

 

Infections are relatively easy to rule out by some simple tests and then treated accordingly.  Demodex mites are easy to rule out with skin scrapes and sarcoptes mites usually need a treatment trial - we use Revolution® at the recommended dose every two weeks for three treatments.  Revolution will also help to rule out flea allergy as well.  

 

Once parasites and infection are ruled out, we only have two culprits on the list of possible diagnoses - food allergy and atopic dermatitis.  Food allergy is fairly easy to rule out but needs to be done in a very specific way. There are some special diets available from vets that can be used to rule out food allergy.  Some examples of the diets we use are Hills Prescription Diet z/d and Royal Canin Hypoallergenic.  Whilst on exclusion diets your dog must NOT receive any other type of food or the results will not be accurate.  

 

In summary: If, after parasites and infection have been eliminated, and your dog’s itch fails to improve significantly after a strict 6-week prescription diet food trial then your dog has atopic dermatitis.

 

What is atopic dermatitis?

 

The word ‘atopic’ comes from the greek work ‘atopos’ which means out of place or extraordinary. In the veterinary medical sense it means that an individual dog (at least their immune system) is having an over-the-top or extraordinary response to substances that are normally harmless (allergens). The strict definition of canine Atopic Dermatitis is:

 

A genetically-predisposed chronic inflammatory and itchy allergic skin disease with characteristic clinical features. It is associated most commonly with antibodies to environmental allergens.

 

The characteristic clinical features are:

 

  • Age of onset before 3 years of age

 

  • Initially no skin lesions (changes), just pure itch

 

  • Typical distribution - front feet and ears most commonly

 

  • Responds well to steroids, though usually temporarily

 

Atopic dermatitis is usually the condition that people (and vets) are referring to when they say that a dog is allergic to grass, pollens, weeds, trees, dust mites etc. It affects 10-15 % of all dogs and together with flea allergy dermatitis, accounts for the majority of itchy dogs we see in practice.

 

How is atopic dermatitis treated?

 

itchy beagleThis depends on the severity of the symptoms.  For mild disease then home treatments may be all that is required.  For moderate disease, steroids (cortisone, prednisolone, dexamethasone) may be used to control symptoms and allow itching to reduce to normal and stop the dog’s self trauma. Steroids have side effects which mean that they are not useful for long term control of atopic dermatitis but they are very useful medications to help settle a flare up.  If the itch recurs shortly after a course of steroids have reduced the itch level to less than grade 2 (remember our itch scale?) then your dog has moderate to severe atopic dermatitis and is a candidate for long term therapy.  

 

Long term therapy is either desensitisation through allergy vaccines or the use of cyclosporin.  If your dog has moderate to severe atopic dermatitis then these treatments will have to continue for the rest of the dog’s life.  

 

Cyclosporin and Apoquel are immunosuppressive medication which are effective at controlling the hypersensitive immune system seen in atopic dermatitis in dogs.  They need to be given regularly (every day or every second day) and are reasonably expensive and probably not quite as effective as steroids at itch relief but they have less side effects and are certainly the medication of choice for long term control of moderate to severe atopic dermatitis.  They can be dispensed by regular GP vets.

 

Desensitisation is a procedure that is performed by a veterinary specialist dermatologist who will do some allergy testing to determine the allergens that an atopic dog is reacting to.  The dermatologist will then formulate an injection containing those allergens and this is injected into the atopic dog.  The effect of having these allergens injected back into the dog is to reduce the atopic dog’s ‘allergic-ness’ to the allergens.  In principle this is the gold standard treatment for atopic dermatitis, though, like cyclosporin is reasonably expensive and owners must be OK with regularly injecting their dog for the rest of it’s life.

 

What are the home treatments?

 

The home treatments that we recommend are ones that have shown some benefit in clinical trials.  We know that there are lots of products in the marketplace that seem natural and have great testimonials but until there has been extensive testing we don’t recommend them.

 

One of the jobs that normal skin performs is to protect us from our environment.  It does this by forming a barrier that is made up of dead skin cells glued together and kept supple with fatty acids and other oils. One of the changes that happens in atopic dermatitis is that this barrier function is reduced and skin dries out and is unable to protect underlying tissues (and the immune system) from microbes and allergens.  This barrier dysfunction seen in allergy effectively allows the immune system contact with allergens and could be responsible for the hypersensitivity seen in atopic dogs.

 

Home treatments basically try to repair the barrier function or to keep it as strong as possible and in a nutshell rely on either moisturising or fatty acid supplementation.

 

Moisturisers:

 

  • Shampoos and conditioners such as Aloveen or PAW Nutriderm (conditioners can be used daily if required)

 

  • Moisturising sprays:
    • PAW Nutriderm Conditioner can be mixed 1 x 200g tube with 400 mls of water to make a non-greasy spray that you can apply to your dog’s affected areas of skin every day
    • Other options are Alpha Keri or QV bath oil diluted 10 mls oil to 500 mls water and sprayed directly onto the skin.  May be slightly oily.

 

Fatty acids:

 

Clinical trials prove that fatty acid supplementation helps to reduce the amount of steroids that an atopic dog requires to keep him/her comfortable.  The dose of fish oil is approximately one 1000mg capsule per 10 kg per day.  You can probably give one 1000mg capsule daily to a 5 kg dog, just check to make sure that there is no resultant diarrhoea.

 

The final word about home treatments is that they help to improve the skin function, not specifically control itch and they cannot be relied on to control itch in a dog that is having a flare up - these dogs need to be seen by a vet.  The best way to use these home treatments is to use them most when the skin is looking good, NOT wait until a flare.

 

What about antihistamines - shouldn’t they work?

 

Antihistamines are used for immediate type allergic reactions like hayfever in people.  Atopic dermatitis is caused by a delayed allergic reaction so it is no surprise that antihistamines have not been found to be very beneficial in canine atopic dermatitis.

 

In summary:

 

Canine atopic dermatitis is a frustrating recurrent and incurable condition that affects a large percentage of our canine pets.  It is not unmanageable, however, and a good understanding of the condition can help us to improve the lives of our itchy dogs.  After all, if your dog’s scratching is keeping you awake, how do you think your dog is feeling?

 

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