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What is Canine Atopic Dermatitis?

Also known as 'atopy', canine atopic dermatitis is an allergic skin condition in dogs that causes itching, which can lead to redness, fur-loss, rough or damaged skin.

Canine atopic dermatitis (cAD) is an allergic skin condition which affects at least 10% of dogs [1,2] and is a common cause of long-term itching. cAD, or simply atopy as it is often known, is the dog version of 'eczema' in people. 

Several different breeds have been shown to be more likely to develop cAD, including Labrador and Golden retrievers, English Springer spaniels, Hungarian Vizlas, Basset hounds, Rhodesian Ridgebacks, Boxers, Chinese Shar Pei, West Highland white terriers, Bull terriers, French Bulldogs, Bichon Frisé and Tibetan terriers [3,4].

Causes

There are many different causes for canine atopic dermatitis, arising from an interaction between the dogs inherited genetics and allergens in the dog’s environment. Although signs of the disease are often similar between dogs, the actual cause may be very different for different individuals.

Studies of genetics of cAD suggest that roughly half of dogs born to atopic parents will develop cAD themselves [5]. The most common environmental allergens thought to be involved with causing cAD are house dust mites [5], storage mites, pollen and mould spores, but food allergies (of various possible types) may also contribute to the condition [4].

Signs of cAD

Canine atopic dermatitis (cAD) is a complex condition, which doesn't occur the same way in every dog, particularly between dogs of different breeds. Symptoms of cAD (also referred to as clinical signs) include itchy skin, which may or may not look red or inflamed, and in severe cases the dogs affected skin may become damaged from scratching, become rough or scaly, and they may lose their fur in that area.

In addition to scratching, itchy skin can cause dog to repeatedly lick the affected areas, which can cause the skin to darken in colour or become red and raw, or they may rub the affected areas. 

There are many different things other than atopic dermatitis that can cause a dog to develop problem skin such as that described above. These include one-off reactions to specific chemicals or plants (such as flea treatment), mange, bacterial infections, food allergies or flea allergies, so diagnosing cAD is often a process of elimination.

It's also important to remember that dogs can also develop 'psychogenic dermatoses', where the onset of clinical signs is connected to a stressful event/situation. In this case the scratching, licking and chewing is emotionally based, as opposed to allergenic and behavioural solutions should be sought.

A dog with canine atopic dermatitis showing a red and itchy muzzle, with no fur loss or damaged skin.
A dog with canine atopic dermatitis showing a red and itchy ficial muzzle, with no fur loss or damaged skin.
 
A dog showing its front right paw. The skin between the toes is red, inflamed and broken from repeated licking
The same dog's front right paw. The skin between the toes is red, inflamed and broken from repeated licking.
 
 

Diagnosing cAD

If your dog is showing any of the signs described above, your vets will be able to diagnose the likely cause of the problem and offer appropriate treatments.

Because of the many possible causes for these symptoms, vets will usually begin by asking you questions about your dog’s skin health and itch-related behaviour, as well as performing a clinical examination. Often, the location of the signs (itching, rubbing, redness) can be very a very useful pointer towards identifying the correct disease. It's important to note the areas affected, and where your dog scratches, rubs or licks.

Skin scrapings may be taken from the affected area in order to eliminate some other diagnoses, or identify secondary problems, such as mange. Cytology or bacteriology may be used to demonstrate presence of infections. When an allergic skin problem has been identified, further tests are available to identify the exact cause, possible allergens include food proteins, pollens, moulds, house dust mites and skin cells from cats and other animals. Using this additional information, specific therapies can be designed. 

References

  1. Lund, EM, Armstrong, PJ, Kirk, CA, Kolar, LM, Klausner, JS.  (1999)  Health status and population characteristics of dogs and cats examined at private veterinary practices in the United States.  Journal of the American Veterinary Medical Association 214: 1336-1341.
  2. Hillier, A, Griffin, CE.  (2001)  The ACVD task force on canine atopic dermatitis (1): Incidence and prevalence.  Veterinary Immunology and Immunopathology 81: 147-151.
  3. Zur, G, Ihrke, PJ, White, SD, Kass, PH. (2002) Canine atopic dermatitis: a retrospective study of 266 cases examined at the University of California, Davis, 1992-1998.  Part I. Clinical features and allergy testing results.  Veterinary Dermatology 13, 89-102.
  4. Picco, F, Zini, E, Nett, C, Naegeli, C, Bigler, B, Rufenacht, S, et al. (2008) A prospective study on canine atopic dermatitis and food-induced allergic dermatitis in Switzerland.  Veterinary Dermatology 19: 150-155.
  5. Shaw, SC, Wood, JLN, Freeman, J, Littlewood, JD, Hannant, D.  (2004) Estimation of heritability of atopic dermatitis in Labrador and Golden retrievers.  Am J Vet Res 65: 1014-1020.

The Itchy Dog Project

School of Veterinary Medicine and Science
University of Nottingham
Sutton Bonington Campus
Leicestershire, LE12 5RD


email: itchydogproject@nottingham.ac.uk