Allergic Skin Diseases

Allergic skin diseases are among the most common, difficult and frustrating conditions to diagnose and treat in veterinary practice.

Is there more than one type of allergy?

Yes, there are at least five common types of allergy in the dog:

a)  flea

b)  food

c)  contact

d)  atopy

e)  bacterial hypersensitivity

The symptoms of these allergies can appear very similar (inflammation and itching) and a dog may have more than one type of allergy simultaneously.

Flea Allergic Dermatitis

Many dogs are allergic to proteins in the saliva that the flea injects in order to obtain a meal of blood, which is essential for completion of the life cycle. In a sensitive dog this causes itchiness, sometimes resulting in very extensive inflammation (dermatitis). 

Once sensitised, due to the hypersensitivity reaction, often the dog needs to receive only a few flea bites to trigger the reaction, which results in continuous pruritus (itchiness).

Treatment may require anti-inflammatory medication and prevention involves effective flea control for all pets in the household as well as environmental control.

Food Allergies

Adverse food reactions can result when a dog develops an allergic response to a component of their diet, for example beef. It commonly results in itching, with or without gastrointestinal signs and sometimes more subtle symptoms such as lethargy or behaviour changes.

Diagnosis is made with the use of elimination diets then re-challenging with the offending food.

Prevention is based on avoidance.

Contact allergy

Contact dermatitis requires direct contact between the skin and the allergen in question. The most common cause in dogs are plants, particularly types of succulent ground covers.  It is seen as inflammation and pruritis associated with the bare skin.

Diagnosis may require avoidance trials or patch testing where a sample of the suspected allergen is left on the skin and the immune response is assessed.

Antiinflammatory medication is used to treat the allergy once it has arisen in combination with shampooing.

Prevention is based on avoidance.

Atopy

Atopy is a complex disease relating to an exaggerated immune response to environmental allergens. It has similarities to hay fever and atopic eczema in people. Once thought to be due to inhaled allergens, the current theory is that contact with allergens via a damaged skin barrier is more important.

Diagnosis involves having supportive history and symptoms as well as excluding all other causes of itch.

Treatment may involve desensitization based on allergy testing results, anti-inflammatory medication, maintenance of the epidermal barrier and treatment of any secondary skin infections.

Bacterial Hypersensitivity

Bacterial hypersensitity is when the dogs immune system over-reacts to the normal staphylococcus bacteria on its skin. It is often secondary to other diseases such as hypothyroidism or flea allergy.

Treatment involves antibiotics and antiseptics as well as treating any underlying diseases.

Urticaria (hives)

Urticaria (hives) is an allergic phenomenon that can result from food, drugs, vaccines, insect bites, stings etc. Single or multiple wheals or swellings of variable size suddenly appear on the skin. Some types of dogs appear to be more susceptible than others.