Itchy Dogs: Atopic Dermatitis

What is Atopic Dermatitis? 

Atopic Dermatis is a form of chronic skin disease caused by allergies.

When your dog (or cat) comes into contact with an ALLERGEN their immune system reacts to it releasing a number of inflammatory molecules, including histamines, which lead to redness, itchiness and general inflammation. Allergens can include pollen, grass particles, dust mites and much more.

Check out this video to help understand the complex process of allergic reactions in less than two minutes.

SO why do these animals react to allergens? This is not completely understood but dogs with atopic dermatitis seem to have a genetic predisposition to reacting, as well as an impairment in the skins natural immune system.

Symptoms

Dogs with atopic dermatitis are pruritic (itchy) and often this itchiness can be very intense. The dogs also develop lesions associated with the inflammatory reaction including red spots which often affect the face, ears, paws and underside of the body. As the itching continues the dogs start showing secondary signs such as alopecia (fur loss), sores, infection, hyperpigmentation (dark skin) and saliva staining.

Diagnosis

Diagnosis of atopic dermatitis can be challenging. Presenting signs are one way of diagnosing the disease. For example a two year old dog that has become itchy every summer since it was a puppy, but then the itching resolves in winter, is displaying signs of a seasonal allergy so atopic dermatitis would be suspected. How ever some cases aren't this black and white - some dogs can be allergic to things like cockroach poop! Which means it is no longer seasonal and they can react all year long.

The most common clinical features of atopic dermatitis are that the dogs present before three years of age, are responsive to steroid (glucocorticoids such as prednisolone) treatments and show the clinical signs described.

The reaction to the injections can be measured to identify allergens.

The best way to diagnose atopic dermatitis is through serological or skin allergy testing. Serological testing involves sending blood away for antibody testing in a laboratory. Skin testing can be done in the clinic and involves injecting small amount of allergens, such as grass and pollen molecules, under the skin and measuring the reaction. This allows us to identify the most common cause of your dogs allergy which may help avoid it and aid treatment.

Treatment  

.Treatment for atopic dermatitis can be costly, long term and sometimes unrewarding. Just like people who suffer from asthma or allergies - once you have it, it is there for life, and not every treatment work for every person.

The first, and seemingly most simple, option is to avoid the allergen. Easy enough if your dog is only allergic to pine trees, but what if, like many, he is allergic to dust mites, six types of grasses and the mould found in most houses? Bit harder...

The second option is helping to modulate the immune system to stop the itching. Anti-histamines can work for around 15% of dogs, and have little side effects. This are a great option IF they work for your dog. Prednisolone, and other glucocorticoids such as triamcinolone, are also commonly used to down-play the immune response and stop itching. The problem with glucocorticoids is they have side effects including increased thirst and hunger, lethargy and although we use them to modulate the immune system this too can have undesired affects such as increased risk for infections. A newer drug on the market with fewer side effects is Apoquel. Aopoquel also modulates the immune system and seems to work well for many dogs.

For mild flare-ups topical glucocorticoid creams, such as cortisone cream, can be used to help reduce the inflammation. These creams have fewer long term side effects than oral or injected glucocorticoids but they can cause thin skin over time and shouldn't be used every day long term.

Finally it is VERY important to treat secondary infections. If your dog has primary atopy but now has big sores all over his body he needs antibiotics. Glucocorticoids alone may help reduce the itching but the infection will just worsen and the skin disease will not heal.

Prevention

The good news is there is a treatment option available that can actually help prevent the signs and treat your pet long-term. This treatment is known as IMMUNOTHERAPY. Immunotherapy involves a series of injections that have been specifically developed for your dogs allergies. This injections help expose the immune system to the allergens in a controlled way, eventually preventing or minimising the reaction. The down side to these injections are they can be costly and a year long commitment must be made to see real improvements.

In terms of other preventatives - as always a good diet will help improve the immune system and coat/skin condition. Fish oil tablets have been shown to help improve the immune system and skin condition, I generally give a 1000mg tablet per 15kg dog.

Medicated shampoos can also help reduce secondary infections, I like shampoos that contain chlorhexidine and miconazole such as Malaseb. These shampoos MUST BE LEFT ON for 10 minutes for them to work. Although oatmeal shampoos have not been scientifically shown to reduce symptoms a nice soothing bath will reduce the surface allergens on your dogs skin and help reduce mild inflammation. I generally recommend once weekly or fortnightly bathing for allergic dogs.

If you have tried tried other methods that have worked well for your pup please comment below! 

In the following weeks I will try to cover all there is to know about the diseases that cause skin issues in our doggies.

Check out the previous blog on Pyoderma