• About Canine Atopic Dermatitis

About Canine Atopic Dermatitis

Atopic dermatitis is one of the most common canine skin diseases, affecting around 10% of the canine population. It is a genetically predisposed inflammatory and pruritic skin disease, most commonly resulting from hypersensitivity to environmental allergens.1,2

Causes1,2

Typical allergens causing atopic dermatitis include house dust mites, pollens and mold spores. Many dogs have multiple allergies and may even suffer from a combination of atopic dermatitis and other hypersensitivities, most notably flea allergy.

Each dog may have an allergic threshold. When the level of allergen exposure is below this threshold, there are no clinical signs. Once this threshold has been exceeded, pruritus and skin lesions develop. Any additional factors that cause skin inflammation, such as the presence of fleas or a microbial infection, may contribute to the development of clinical signs. These are known as 'flare factors'.

Any breed of dog may be affected but some are more prone than others. The breed incidence varies geographically as genetic factors contribute to the susceptibility of certain breeds to develop atopic dermatitis. Some of the breeds most commonly reported to be affected by atopic dermatitis include:

  • Terriers, especially West Highland White Terriers and Staffordshire Bull Terriers
  • Boxers
  • Labrador Retrievers, Golden Retrievers
  • German Shepherds

Clinical signs1,2

Signs of canine atopic dermatitis usually first appear between 6 months and 3 years of age.1 Initially there may be no visible lesions or just erythema. Many of the signs that develop are due to secondary damage caused by self-trauma.

The disease may start seasonally, but usually this progresses to non-seasonal disease, often with seasonal exacerbations. The clinical signs often increase and decrease in severity, depending on the level of exposure to allergens and the presence of secondary infections or concurrent allergic diseases.

Many of the signs that develop are due to secondary damage caused by self-trauma. Other lesions such as pustules, crusted papules and epidermal collarettes may develop due to secondary infections. Signs may also be exacerbated or altered by secondary factors such as the presence of fleas or infections.

The degree of pruritus is typically moderate (for example rated 5-7 out of 10). Secondary infections often increase the degree of pruritus and may make the pruritus poorly responsive to treatment for atopic dermatitis.

Typically, lesions start at friction areas and skin folds:

  • Face – around mouth, around eyes, inside the pinnae
  • Feet
  • Axillae
  • Groin and perineum
  • Flexural surfaces (front of elbows, front of hocks)

Some dogs present with only recurrent otitis externa. In chronic cases the skin develops alopecia, excoriation, lichenification and hyperpigmentation.

Diagnosis and treatment

Dogs that suffer from chronic atopic dermatitis may have a poor quality of life if the disease is not diagnosed, treated and managed correctly.1,2 Veterinarians may follow the 3 steps to continuous comfort and advise pet owners on allergen avoidance.

Treatment options1,2

There are a variety of treatment options for canine atopic dermatitis and a combination of different treatments is often needed to manage it, particularly when it suddenly flares up.

The four main treatment types are:

  1. Treatments that aim to reduce the allergens responsible for causing atopic dermatitis
    • Low dust mite bedding
    • Regular shampooing (to remove allergens) or treating with rinses and topical anti-pruritus solutions. They are often effective when used with other treatment types
    • Changes to the diet
  2. Treatments to reduce flare factors
    • Comprehensive flea control
    • Regular sampling to check for bacterial or Malassezia infections and treatment for these if required
    • Antibiotics and antifungals to fight secondary infections
  3. Treatments that aim to control the allergic reaction
    • Treatments that improve the skin health, for example food supplements. These contain essential fatty acids that can help reduce pruritus in some dogs. They have few side effects, and because of this are often used as a supplementary treatment
    • Antihistamines may help control pruritus; however, they rarely provide adequate control on their own. They may be useful in mild disease and/or when used as a preventative. Furthermore, since dogs respond differently to different antihistamines, several types may have to be prescribed in an attempt to find an effective one
    • Corticosteroids are generally effective at reducing or eliminating pruritus; however, they may also be associated with a number of side effects, both in the short and long term. Patients may develop polyphagia, polydipsia and polyuria. Skin thinning, liver damage, and skin and urinary tract infections may also be associated with prolonged use.3 Therefore, steroids are better used for the short-term control of pruritus and provided they are used appropriately (i.e. at the lowest dose, after other complicating diseases have been controlled), side effects can usually be minimized
    • Atopica (cyclosporine) is an immunomodulator that targets the immune cells involved in the allergic reaction and can be used for long-term control of the allergic response in a dog's skin. This oral treatment has been proven through extensive clinical trials to be well tolerated and effective in reducing the pruritus and skin lesions associated with atopic dermatitis. It may reduce the need for simultaneous treatment with other medication and may be given life-long if necessary4
  4. Treatments that aim to prevent future flare-ups of atopic dermatitis
    • Immunotherapy involves injecting the dog with increasingly large doses of allergens (identified by an intradermal or serology test). Immunotherapy via injections or oral administration is done over time and the dog may take several months to respond to the treatment. This therapy may prevent recurrence of flares, and may need to be given life-long.1,2

References: 1. Olivry T et al. Vet Dermatol (2010); 21:233-248. 2. Scott-Muller and Kirk 6th ed (2001);580-581. 3. Ferguson DC et al. In: Riviere JE and Papich MG (eds) Veterinary Pharmacology and Therapeutics, 9th ed (2009);771-802. 4. Steffan J et a. Vet Dermatol (2006); 17:3-16. 5. Olivry T and Sousa CA. Vet Immunol Immunopathol (2001);81:311-316.