Atopy is an incurable disease that can only be treated for comfort – recognise the symptoms and understand the treatment
Atopy is the most common allergic disease we see in dogs. The condition also exists in cats, but it is much more difficult to diagnose.
Most cases start between 6 months and 3 years of age, although occasionally they can be seen either side of this age range. The current definition of the condition is “an inherited pruritic skin disorder characterised by the production of allergic antibodies to environmental allergens”. However, the pathogenesis is complex and involves several abnormalities in the skin, the most important one being a defective skin barrier.
The classic signs are an itch and diffuse erythema (red inflamed skin) affecting the inside of the ear flaps, the upper ear canals, the skin around the eyes and muzzle, the underside of the body and the feet. Many cases will only show one or two of these signs and approximately 5-10% of cases show the inflammation and itch only in their ears. Affected dogs will often scratch and rub their faces and chew at their feet.
The disease is complicated by the presence of secondary bacterial and yeast infection, and these infections will also contribute greatly to the amount of pruritus (itch) the dog is suffering with and also change the appearance of the skin. You may notice that the skin looks scaly and crusty.
As the condition progresses, more chronic changes can occur in the appearance of the affected skin. It becomes thicker and more pigmented, sometimes almost black.
Much research has been done on this disease over the last 10 years and it has been discovered that dogs suffering with atopy have different skin to non-atopic dogs. They have a defect in their skin barrier due to differences in the lipid barrier. These defects can allow environmental allergens such as house dust mite proteins and pollens to permeate the skin and be picked up by cells which then present them to the immune system.
The diagnosis of atopy is based on history, age of onset, clinical signs and after ruling out all other causes such as parasites, food allergy and contact dermatitis. It is an incurable disease and although the ultimate goal with treatment is to abolish all symptoms entirely, a more realistic goal is to allow the patient to be ‘comfortably itchy.’ There is no ‘one size fits all’ treatment for this disorder and each case is treated individually according to the severity of the disease and the resources of the owner.
Treatment with antihistamines and essential fatty acid supplements and other pharmaceuticals may help only as an adjunctive treatment, for instance, lowering the dose of steroids that are required. Intermittent treatment with antibiotics and antifungals (both topical and systemic) may be necessary throughout the life of an atopic dog. Topical therapy to improve skin barrier function is also necessary. All affected animals should be placed on a permanent programme of flea control as a picking up a flea can raise the “pruritic threshold” below which an animal may be itch free. Regarding drug therapy, steroids are effective and cheap, but carry the risk of a multitude of long term side effects. Cyclosporin is usually very effective but is also very expensive. In January 2014, a brand new drug, Oclacitinib, became available. This is more targeted at reducing the itch, is fast-acting and effective in most cases and has a cost between steroids and cyclosporin.
One of the best treatments to try is Allergen Specific Immunotherapy (desensitisation), based on the results of allergy testing, Intradermal Skin Testing or Serological Allergy Testing (blood tests), or a combination of both. This can reduce the severity of symptoms by at least 50% in 75% of affected individuals. We have a full range of allergens for intradermal skin testing at the clinic. Immunotherapy is usually given by injection, building up from every 2 weeks to every 4 weeks.
We are now also offering sublingual immunotherapy (SLIT), where the allergens are given by a pump that delivers a small amount of the allergen mixture under the tongue; this is more owner-intensive, but has been shown to work for some cases that don’t respond to injectable immunotherapy and the allergens do not have to be kept refrigerated.
There are a very small proportion of dogs which fit all the criteria for canine atopy, but fail to produce reactions either on IDST or have positive allergen specific IgE on blood testing. These individuals are said to be suffering from “atopic-like dermatitis” and unfortunately, are not candidates for immunotherapy, although can respond to the other therapies given to atopic dogs.