Within Veterinary Medicine it is well accepted that allergic skin disease in dogs has a hereditary basis. Or at least, there exists predisposition towards allergic skin disease with certain breeds of dogs. This underlying inherited basis may have a complex pattern of inheritance however. That is to say, multiple genes may be involved.
What sort of skin disease are we talking about?
“Canine atopic dermatitis” or “atopy” is defined as a skin hypersensitivity condition caused by allergies to (otherwise harmless) environmental substances (known as “allergens”). Its prevalence is cited as affecting at least 10% of the dog population. We recognise and acknowledge that certain breeds are susceptible to developing atopy and such breed predisposition further reinforces an underlying genetic basis to the disease. It is also important to stress however, that allergic disease may also develop within any dog, irrespective of their breed.
Additionally, for a dog to develop atopy, there must also be exposure to the causal allergen(s). The disease thus develops due to a combination of both a genetic predisposition AND environmental factors. Furthermore, not only must the allergen be present within a dog’s environment, the dog must also have had repeated contact with the substance over a period of time, in order for the allergy to develop.
So which breeds are affected?
Breeds commonly affected with atopy include Labradors, Golden Retrievers, German Shepherds, Poodles, Spaniels, Staffordshire Bull Terriers, French Bulldogs, Jack Russell Terriers and West Highland White Terriers. In the vast majority of cases, clinical signs typically develop within the first 1 – 3 years of a dog’s life. Depending on the allergens involved, the time of year a dog may be affected can vary.
So what exactly happens in atopic dogs?
Essentially, an atopic dog has an over exaggerated and excessive immune response to certain substances (those “allergens” we mentioned earlier). This response will develop after repeated allergen exposure.
Years ago, it was originally thought that the allergens gained entry to the body by direct absorption across the skin itself. This has now been proven not to be the case. Actually, the allergens are either inhaled or ingested – and gain access to the body by crossing a mucosal surface.
In response to the allergens, the body produces high levels of immunoglobulin antibodies (IgE). Through several complex interactions involving the immune system, various chemicals (particularly histamine) are produced. These chemicals cause the dog to feel itchy and unsettled.
And what are the allergens?
The most common allergens include (microscopic) mites – house dust mites and storage mites. Whilst most normal dogs are capable of tolerating such mites, in atopic dogs, they cause an inappropriate immune response, such as that described above.
As I always explain to owners, house dust mites are present in all of our homes (and a diagnosis of house dust mite allergy in a dog is not to be taken as an insult to their standard of living or cleanliness!) However, dust mites do live in soft furnishings and carpets and thrive particularly well in damp, humid and poorly ventilated conditions. By putting a number of management strategies in place within the home, the allergic “burden” of dust mites can potentially be significantly reduced.
Storage mites are often associated with the storage of dry pet food. Exposure can be reduced with some straightforward changes.
Common outdoor allergens include grasses, certain trees and also weeds.
Dependent on the nature of the allergy, dogs may initially show a seasonal pattern to their symptoms. For example, a dog with grass allergies may worsen during the summer months when the grass grows vigorously. Conversely, a pet with a house dust mite allergy may well be worse in winter when spending more time inside the home along with reduced ventilation.
And what are the symptoms?
Moderate or severe itchiness (pruritis), is the hallmark of allergic disease. Dogs may lick, chew, rub, nibble or scratch themselves. Certain areas on the dog’s body may be affected; particularly the face, ears, armpits, feet and lower aspects of the limbs. The skin may become red, inflamed and sore. With persistent symptoms, hair loss (alopecia) is seen alongside pigmented or darkened skin (hyperpigmentation).
Because the dog will relentlessly itch or lick the affected areas, secondary bacterial and yeast infections are common. Whilst all dogs have bacteria and yeast on their skin, when the skin surface is healthy and intact, they are “commensal” organisms and cause no harm. Change the situation to an atopic dog however, who is tirelessly licking or chewing a certain area of skin, then skin damage encourages localized infections. Such secondary infections themselves, also contribute to the itch factor and so need to be treated as part of the management of the disease.
In larger breed dogs, the main symptom of atopy may just entirely relate to otitis externa (disease of the outer ear canals). Ear disease causes ear pain and irritation, alongside redness to the skin and often a dark brown or yellow discharge. Shaking the head and scratching of the ears are symptoms. Atopy is therefore worthy of consideration in any large breed dog with persistent or recurrent ear disease.
In some affected animals, allergic responses will also be seen in the eyes and respiratory tracts, causing conjunctivitis (sore eyes) or sneezing.
As a final note…
All that remains to say, is to remind you that unfortunately, due to its hereditary nature, atopy is a long-term disease. Controlling symptoms is realistic, curing the disease is not. These days, vets have various treatments available for atopic dogs and these should greatly reduce symptoms and increase the quality of life for your companion.
The disease may wax and wane through the year; however, depending on the prevalence of and exposure to, the specific allergens that your dog reacts to. Multiple management strategies (to minimize exposure to allergens) and treatments (injectable, oral and topical) are likely to be required.
Understandably, sometimes reducing the exposure to an allergen proves difficult – certainly to an outdoor allergy of say grass. In such instances, a reliance on long-term oral or injectable medication is likely to be required.
Excellent ectoparasite control (flea, tick and mite prevention) should be continually sustained throughout the year. An infestation with any of these parasites will only cause to act as a “flare factor” and worsen the itch.
Share your experiences or ask our vets any questions regarding skin conditions in your canine friend in the comments below.