Allergic Dermatitis

Symptoms

Allergic dermatitis (commonly referred to as eczema) can be manifested as excessive scratching or biting of the skin, chewing of the feet, hair loss at the base of the tail and redness of the skin.  Recurrent ear infections and scratching of the ears can sometimes be the only symptom.  In some animals it is a seasonal problem starting in spring, in others it is a continual year round problem.

Causes

Regardless of the cause of the allergy, the symptoms are often similar.  Dogs and cats with allergic dermatitis are often sensitive to flea bites, but there are other agents which can be incriminated.  There are many incriminating agents that generally fall into one of the following categories:

• Atopy e.g. pollens, grasses, dust, absorbed through the skin or inhaled. Similar to human hay fever.
• Parasitic e.g. fleas (very common)
• Food e.g. beef or chicken
• Contact e.g. carpet fibres, grasses

Complications

The itchy skin often results in severe self-mutilation where the damaged skin becomes infected with bacteria (very early) and/or yeast.  Long standing, untreated cases can have severe skin infections.  Dogs with severe skin irritation may go off their food or become short tempered with humans and other dogs.

Diagnostic Approach

Allergic skin disease is one of the most frustrating conditions to get to the bottom of and treat successfully.  A successful outcome depends mostly on the correct communication between pet owner and veterinarian and regular monitoring of the condition.  A logical, standardized approach to all cases is necessary for a good response to treatment.

The first step is the recording of a complete and detailed history – What diet is your pet on?  What flea control?  Where does he/ she go for walks?  How long has the condition been going for?  Any previous medications that have been used?  These are just some of the questions we may ask in order to best understand your pet’s allergy.

Secondly, a full clinical examination will be done to look at the skin lesions – where do they occur on the body?  Other parts of the body and other organs will be examined to make sure there isn’t an underlying problem present (this can be very difficult to determine at the time of presentation as allergies may often disguise other conditions).  Often underlying problems can only be fully investigated once the allergy has been attended to.

Thirdly, comes the diagnostic investigation and this may include some skin tests (where we have a look for any parasites as well as any infection).  If other underlying causes are suspected (e.g. hormonal problems or other metabolic problems), then blood tests may be necessary as well.

The last part of the diagnosis involves response to treatment (see below). In some cases that do not respond appropriately, further tests may be necessary such as intra-dermal sensitivity testing.

Treatment

This is often a stepped and logical approach:

1. Infection

Any traumatized skin is generally infected with bacteria and may even have a chronic yeast infection present.  This infection can cause the skin to be even more itchy than it originally was.  Antibiotics are generally dispensed for this.  An anti-fungal wash can additionally be used.  One can also use anti-bacterial washes for some chronic cases.

2. Fleas

In most cases of skin allergies, an appropriate flea control program is essential. Even if there are no fleas evident, one still needs to address this, as any flea infestation, no matter how small, can exacerbate the allergy.  Speak to one of our vets for the recommended flea treatment plan for your pet.

3. Food Elimination Trial

In cases where a seasonal occurrence of symptoms is not obvious, a hypoallergenic food trial will likely form part of both the diagnostic and treatment plan.  A minimum of 8-10 weeks on a unique protein source food, is necessary to rule out food as a potential cause or exacerbating factor.

Royal Canin Hypoallergenic is a commercially available food that is designed for this and is available in our practice.  Other home cooked suggestions include:

• Kangaroo meat
• White Fish
• Rabbit
• Sweet Potato
• Pumpkin

It is very important during this food trial that you feed your pet ONLY the suggested food.  One small treat, one small left over from a meal, is all that is needed to negate the process. 

4. Drug Treatment

The most commonly used drugs to aid in the treatment and reduce clinical symptoms are cortisone and anti-histamines.  Cortisone can be taken in tablet form or in a local spray/ ointment.  Anti-histamines are very variable in their efficacy and it may be necessary to try various different types of anti-histamines, before finding one that works for your pet.  The latest research seems to show that anti-histamines together with omega 3 fatty acids (cold fish oils or evening primrose oil) act synergistically (i.e. enhance each others effects).  So using them together may be of great benefit.

A drug gaining more favour in treatment is cyclosporine (Atopica).  Whilst this drug can work out to be expensive (especially in larger breeds), it’s advantage lies in the fact that cortisone is generally not necessary and therefore the side effects of long-term cortisone use are eliminated.

5. Local Skin Treatment

Reducing the “itch threshold” can be aided by the use of localized products on the skin.  We recommend the use of a spot on product called “Essential 6” which is a fatty acid applied once weekly in a spot-on fashion.  This helps in preventing dry skin occurring.  Cold water baths can also be used to “cool” the skin.  As mentioned above, cortisone sprays (Cortavance) or ointments (Elocon) can also be applied directly onto the skin thus avoiding tablets and their side effects. 

6. Desensitization

With specific cases that have undergone intra-dermal testing, a vaccine can be developed which is given regularly in order to ”desensitize” your pet to various allergens. 

7. Other

Fatty acids (cold fish oil capsules) are often used in the treatment of allergic skin conditions and may go a long way toward reducing the necessity for certain drugs like cortisone.

Royal Canin Skin Support and Royal Canin Sensitivity Control are prescription diets for pets with skin allergies, containing specific supplements known to improve the overall health of the skin, increase the skin’s natural defences and promote healing.

Weight Control may be recommended as overweight dogs are more susceptible to dermatitis.

What else can I do?

Other possible ways that you can aid in the prevention of allergen exposure at home include:

• Wash your pet’s bedding once weekly. In some cases it may even be best to change the bedding completely – foam bedding is best for allergic cases.
• Avoid pollen allergens – keep your pet inside on high pollen count days, especially if windy. Most plants pollinate between 5am and 10am in the morning – take your pet on evening walks.  Use a foot bath after walks to remove allergens from feet and bath once to twice a week to remove pollen allergens from coat.
• Maintain stringent long-term flea control.
• Regular check-ups are necessary, especially in the first 3-6 months of treatment. It is during these check ups that your vet will make adjustments to treatment and monitor progress and eventually institute a long-term plan/ approach.
• Attend to any flare-ups quickly before secondary problems set in, otherwise it is likely to result in a need to start all over again with the treatment etc.
• Understand that communication with your vet is paramount to a successful outcome. All these cases require some form of long-term and often life-long, treatment in order to achieve control of their condition.