What is it?
Also known as "Atopy", Atopic Dermatitis is the second most common allergic disease in dogs, with as many as 15% of dogs affected. It may best be described as a condition where the dog's immune system is hyperactive, giving them a predisposition to developing allergies to multiple different harmless chemicals (or "allergens") in the environment.
What causes it?
Atopic Dermatitis is a genetic condition, although the exact mechanism isn't well understood. It causes a predisposition to developing allergies, and may also make the skin more susceptible to bacterial infections as well. Affected dogs may become allergic to pretty much anything - typically we'd expect to see allergies to grass, tree and other plant pollens, harmless mites (like dust mites or storage mites), as well as foodstuffs (typically protein sources such as beef or soy) and other ubiquitous substances. Occasionally, however, dogs develop much more unusual allergic reactions, for instance to perfume or even rice.
What dogs are at risk?
Although Atopy is seen in many breeds, the most heavily predisposed is the West Highland White Terriers. Other breeds with a higher than average chance of developing the condition include Staffordshire Bull Terriers, Boxers, Labradors, Golden Retrievers and German Shepherd. The symptoms always appear first in young dogs - although they may be so mild at first that they aren't noticed or diagnosed until the dog is older.
What are the symptoms?
Atopy results in what we often call "allergic skin disease"; however, it is often more severe and harder to manage than other skin-based allergies. The most characteristic symptom is violent itchiness - often dogs will rub themselves raw trying to scratch - which is usually worst on the face, in the armpits and on the feet. Other symptoms often include repeated "ear-infections" (because the ear canal is lined with skin!), and skin infections ("pyoderma"). The end result is hair loss, reddened, sore or scratched skin, and then infection with pustules forming.
How is it diagnosed?
Unfortunately, it is very hard to diagnose atopy conclusively - we generally work by "ruling out" other options! That said, the most powerful diagnostic technique in our armoury is the 2009 Favrot Criteria, which comprise a list of "check-points" we score the dog against. If 5 are met, there's an 80% chance the dog is atopic; if we can match 6, that goes up to 90%. There are different versions of the test, but the criteria usually include: (1) symptoms appearing before three years old; (2) the dog mainly lives indoors but is still affected; (3) the itching improves if steroid medication is given; (4) the itching occurs before the hair loss or rash; (5) the front feet are affected; (6) the centres of the ears are affected, but (7) the edges are not; and (8) the dog's belly is more severely affected than their back.
How can it be treated or managed?
Sadly, there is no cure for Atopic Dermatitis. However, it can be managed, and there are a wide range of different management options available. The key (if possible!) is allergen avoidance - if your dog isn't exposed to any of the allergens they overreact to, they won't develop symptoms. Allergy Tests (which may use a blood sample or a skin-prick test) can tell you what your dog is reacting to, so you can take steps to minimise their exposure. Skin treatments can be very useful, such as fatty acid sprays and soothing shampoos; but medications are usually essential. The mainstay of management is generally a drug called ciclosporin, which "tunes down" the immune response, but other options include steroids (effective but often with severe side effects if used for too long) and oclacitinib (an anti-itching drug). There's also the possibility in many cases to use immunotherapy with a vaccine that helps to "teach" the immune system that a particular allergen is harmless. In most cases, no one approach will be successful on its own, and managing a dog with Atopy requires experimentation and committment to find the combination of techniques that works for them.
Can it be prevented?
There is no preventative medication or screening test at the moment, unfortunately, for this genetic disease.