Why is my dog itching? A guide to atopic dermatitis

Seeing our pets scratching excessively can be extremely distressing, and whilst there are many possible reasons for itching to occur, underlying allergic disorders are often found to be the cause. Similarly to humans, allergies in our pets occur due to the immune system perceiving normally harmless substances as a ‘danger’. In response the body mounts an attack against the ‘intruder’, resulting in the manifestation of symptoms. The symptoms that arise in our pets, however, usually express as disorders of the skin and ears rather than the respiratory (breathing) signs we tend to associate with allergies in people.

‘Atopic dermatitis’ is the name given to a chronic[JM1] (long lasting) allergic disease that occurs when environmental allergens, such as pollens and dust, stimulate an extremely exaggerated immune response causing much more severe symptoms compared with ‘simple’ allergies. This condition can be tricky to understand, so here at Protexin Veterinary we have put together this handy guide to give you more information on the causes, symptoms and long-term management of the condition.

 

WHAT IS ATOPIC DERMATITIS?
It is believed that approximately 10-15% of the entire global dog population is currently affected by atopic dermatitis (AD), an extremely complex skin disease causing severe itching and extensive skin lesions. Although research is constantly evolving, AD is thought to occur due to a combination of an overactive immune system reacting to otherwise harmless environmental substances (plant pollen, house dust mites, fungal spores), and a structural problem within the skin itself, preventing skin barrier protective mechanisms from forming as they should.

Imagine the skin barrier as a tough brick wall; the skin cells (keratinocytes) are represented by strong, sturdy bricks that are held tightly together by a waterproof fatty substance (lipid matrix) we can liken to mortar or cement. In dogs with AD, however, the skin barrier is like a crumbling brick wall; there is a shortage in the components that make up the mortar (lipid matrix), and the bricks (skin cells) themselves are weak and fragile. This means that substances in the environment can easily breach the body’s primary protective barrier (the skin) and trigger a cascade of allergic reactions that can lead to intense inflammation and itching. This itching results in further damage to the skin (via self-trauma and scratching), creating more inflammation; hence a vicious itch-scratch cycle begins…

Another consequence of this weakened and damaged skin barrier is that populations of microorganisms, normally coexisting happily on the skin surface, become imbalanced (known as a dysbiosis). This can allow overgrowths of ‘bad’ bacteria and yeasts to occur, which can result in infections and further exacerbate the inflammation.

Dogs usually develop signs of this disease between 6 months and 3 years of age and any breed can be affected; however, there does seem to be a hereditary factor with certain breeds and family lines being much more prone to developing AD than others. These include (but are not limited to):

  • West Highland White Terrier
  • Golden Retriever
  • Labrador Retriever
  • German Shepherd Dog
  • Boxer
  • English and French Bulldog
  • Pug
  • Lhasa Apso
  • Shih Tzu

 

WHAT ARE THE SIGNS AND SYMPTOMS?
The most common sign of AD in dogs is itchiness. It might surprise you that itching can present itself in many forms so be on the lookout for: licking, nibbling, chewing or your pet rubbing their face or body along the floor! Below is a list of the most common signs and symptoms we associate with AD:

Itching, chewing, scratching and rubbing (most commonly the ears, face, tummy, front of the forelegs, feet and armpits but varies with breed)
Licking (especially paws)
Redness and rashes
Skin infections – these can appear as skin rashes, red patches, fur loss and scabs/non-healing ‘wounds’
Hair loss/thinning
Thickened scaly skin
Skin changing to a darker colour (hyperpigmentation)
Ear infection/inflammation – this may present as excessive head shaking, soreness when touched around the ears, ear discharge (with or without a bad odour), redness and/or crusting and scaling of the ears. Sometimes this may be the only complaint and allergies can often be a cause of reoccurring ear infections
Conjunctivitis (redness and inflammation of the conjunctiva in the eye)

Whilst the above signs may indicate your dog is suffering from AD, they can also be associated with many other disorders, so if your pet is showing any of these signs we recommend consulting your veterinary surgeon as soon as possible.

 

HOW IS ATOPIC DERMATITIS DIAGNOSED?
AD is a difficult condition to identify and is often a ‘diagnosis of exclusion’. This means your vet will only be able to confirm AD by ruling out other common disorders that present with similar symptoms, and then by trialling response to treatment and management protocols.

To begin with, your vet will ask you questions about your pet and examine them carefully. They may also recommend performing a few tests to help rule out other causes.

There are certain characteristic features which vets look to identify when diagnosing AD, such as:

  • The ears flaps are affected (excluding the edges)
  • The front paws are affected
  • The symptoms started before the age of 3 years
  • Your dog keeps getting reoccurring infections on the skin or in the ears
  • The itching will reduce when your dog is given certain medications (steroids)
  • Your dog lives mostly indoors
  • The skin on your pet’s back is NOT affected
  • The itching began initially without any changes to the skin (no redness or scabs)
  • There is no single test that can identify AD, but if your dog has five or more of the above features then a diagnosis of AD becomes much more likely. It’s important to note, however, that symptoms can differ between different breeds, and even animals of the same breed!

It is extremely important that your vet is able to rule out all other causes of itching such as parasites (fleas, mites), infections and contact or food allergies. Your vet may discuss performing a diet trial to rule out food allergies; however, it is possible for your pet to have both a food allergy and AD at the same time.

A note on allergy testing
You may have heard of allergy testing for pets, but this cannot be used to diagnose atopic dermatitis and is not a reliable way to test for food allergies. However, it can be helpful in finding out if your dog has sensitivities to environmental allergens (pollen, dust mites, mould), and the results can be used to create an individualised injection programme (allergen specific immunotherapy) which acts to desensitise your pet to their allergic triggers. It is important to understand that this is not a cure for atopic dermatitis; however, in combination with other long-term management therapies, it can help reduce your pet’s symptoms and allow your vet to lower doses of other medications.

 

TREATMENT


Any causes of a sudden flare-up of AD should be identified and eliminated, or exposure to the culprit minimised, if possible. This could be recent exposure to certain pollens (walking in different fields), a change in diet, or fleas and other insect bites that cause your pet’s immune system to overreact. Removing these allergens or reducing exposure can help prevent the frequency or severity of flare-ups.

However, the most important thing to understand is that the treatment of AD is long term, and will require ongoing medication and management. One of the difficulties with AD is that it can flare up and settle down at various times throughout the year and change during your pet’s life; so, whilst at certain times it may appear as if your pet is ‘cured’, it is still extremely important to continue with their treatment plan and proactively reduce flare-ups from occurring.

Medical management
During a sudden flare period, your dog may be prescribed the following medications by your vet to make them more comfortable, some of which can reducing itching in as little as 12 hours!

  • Anti-itch medications – these are particularly important in breaking the itch-scratch cycle to prevent your pet causing further damage to their skin. Often these drugs are required as part of a long-term treatment plan; however, nowadays there are many options which are very safe and have little or no side effects
  • Anti-itch sprays
  • Topical therapies – including shampoos, foams, mousses and lotions (we will talk more about this later)
  • Antibiotics (if there is evidence of a secondary skin infection)
  • Ear medications (if there is inflammation or infection in the ear canal)

Seeing our pets scratching excessively can be extremely distressing, and whilst there are many possible reasons for itching to occur, underlying allergic disorders are often found to be the cause. Similarly to humans, allergies in our pets occur due to the immune system perceiving normally harmless substances as a ‘danger’. In response the body mounts an attack against the ‘intruder’, resulting in the manifestation of symptoms. The symptoms that arise in our pets, however, usually express as disorders of the skin and ears rather than the respiratory (breathing) signs we tend to associate with allergies in people.


Lifestyle and long-term care
So, what else can you do to help support your pet and help reduce the frequency of these flare-ups? A combination of therapies is what we call a multimodal approach, and holds the key to successful management of AD.

Topical therapies

Reducing the itch and inflammation

Bath time will become a regular activity for you and your dog during flare-ups, possibly even one a week! Shampooing is important for several reasons; certain products can reduce itching by moisturising and soothing the skin, whilst additionally removing allergens (such as pollen) and debris from the coat to limit your pet’s exposure. Other shampoos may be prescribed by your vet to treat specifically diagnosed bacterial and/or yeast infections, and in these cases bathing may need to increase to as often as three times weekly until the levels of yeast/bacteria are back under control.
More recently, foams, moussesand wipes have been developed to help make your life a little easier, as we know bathing can be time consuming and particularly difficult in large breeds.
There are many topical therapies on the market and the frequency they should be used will depend on numerous factors including your pet’s particular skin condition, severity of symptoms and causes of flare-up, and the specific products being used at that time; as such it’s essential to ensure your pet is being regularly monitored by your vet who can advise on protocol alterations based on how your pet is responding to therapy.

 

Skin barrier support

A huge part of the management of AD comes down to repairing and maintaining the skin barrier (rebuilding the crumbling brick wall that we mentioned earlier). Not only does this limit the number of substances able to cross the ‘wall’, but it also creates a waterproof barrier meaning water cannot escape and the skin remains hydrated. However, even once repaired, brick walls need ongoing upkeep to stay standing and in the same way the skin needs continual support to stay healthy. Regular maintenance of the skin barrier can help reduce doses of other medications, decrease the frequency and severity of flare-ups, and therefore improve your pet’s quality of life.

 

Ceramides arethe predominant type of fat found in the lipid matrix (cement) of the skin barrier, making them an important molecule for skin health. Topical ceramideproducts act to directly replace the ‘cement’ in between the bricks, allowing them to become tough and strong again. Consequently, moisture is locked into the skin, helping to prevent it from becoming dry, itchy and flaky. Regular application of ceramide-containing products can form part of a successful multi-pronged approach to keeping your pet’s skin condition under control throughout the year.

 

Oral skin supplements

Whilst less effective at helping during sudden flare-ups of itching, supplements and diets high in essential fatty acids have been shown to exert a beneficial effect on the skin barrier, and coat quality, when given for at least 2 months. The addition of essential fatty acids (omega-3 and omega-6) can increase the lipid matrix (cement) found in between skin cells, which we know is decreased in many dogs with AD and is vital for normal skin barrier function. These fatty acids need to be given in high doses, therefore you should look to source a good-quality essential fatty acid supplement, or enriched diet, to ensure adequate amounts are present. However, please discuss any form of supplementation with your vet first, as if your pet is overweight, has problems related to vitamin metabolism (especially vitamin A) or has had any previous problems with pancreatitis, then supplementing with high doses of essential fatty acids may not be suitable and could potentially even be harmful.

 

Limiting exposure

Dust mites – house dust mites are one of the most common (worldwide) allergens that can trigger AD. To help reduce exposure, be sure to regularly wash bedding and blankets (either use a pet-safe sensitive detergent or no detergent at all) and frequently groom/brush your pet to remove excess dust and environmental debris from their fur.
Pollens – wipe down your pet’s coat with a damp cloth after each walk/trip outdoors, concentrating on the legs, paws, face and belly (this can help remove pollen spores and grass seeds). Groom or brush your dog regularly – this can help to remove any shedding fur and environmental debris, whilst also encouraging blood flow to the skin, and can aid in alleviating itching.
Fleas – dogs with AD can be predisposed to developing a sensitivity to fleabites – this means if your pet is repeatedly bitten by fleas, they are more likely to develop an allergy to the flea’s saliva (in addition to anything else they are already allergic to!). Therefore, year-round treatment with an oral anti-parasite product is recommended, as topical ‘spot-on’ treatments are likely to be washed off due to the frequency of bathing that is also required.

Although atopic dermatitis can be a difficult condition to manage, the above information should equip you with a better understanding, allowing you and your vet to work together to form a successful multimodal treatment plan.

Through a combination of prescribed medications, topical therapies, skin barrier maintenance and lifestyle management, your pet can continue to live a long, healthy and happy life.

 

Reference

1. Hillier A, Griffin C. The ACVD task force on canine atopic dermatitis (I): incidence and prevalence. Vet Immunol Immunopathol 2001; 20:81(3-4): 147-51

Meet the Author

Pippa Coupe

Pippa graduated from the University of Bristol in 2015. She spent the following five years practicing as a small animal vet in Somerset, and then Buckinghamshire before joining the ADM Protexin Vet team at the end of 2020. Pippa has a keen interest in nutrition, gastrointestinal health and the importance of the microbiota.

Outside of work, Pippa is a keen runner and member of her local CrossFit box. She also enjoys baking and going for long weekend walks with her incredibly lazy Labrador, Ted (who is less enthusiastic about the long walks and would prefer to stay in bed).