The most common problem owners present their pet to the veterinarian has to do with skin conditions. Most of these are chronic conditions that can be controlled long term to decrease the incidence of secondary ear and skin infections. Other conditions are primary infections or infestations such as flea infestation, mange, bacterial folliculitis or dermatophytosis (commonly know as ringworm). A thorough physical examination, history of illness and a few simple tests usually are all that is needed to uncover the cause of the underlying problem.
Of all the skin conditions we see allergic inhalant dermatitis (atopy) is the underlying cause in a vast majority of dogs and cats with skin problems. Controlling the allergy thereby controls the secondary problems.
What is an allergy?
An allergy is a state of over-reactivity or hypersensitivity of the immune system to a particular substance called an allergen. Most allergens are proteins. The allergen protein may be of insect, plant or animal origin. Initial exposure of the dog, or more likely multiple exposures, to the allergen may over-sensitize the immune system, such that a subsequent exposure to the same or related allergen causes an over-reaction. This means that the immune response, which normally protects the dog against infection and disease, can actually be harmful to the body.
The immune reactions involved in allergies are quite complex. Most reactions involve an antibody in the blood called Immunoglobulin E (IgE). In an allergic reaction the allergen protein molecules combine with IgE antibody molecules and attach to a type of cell called mast cells, found in many tissues throughout the body. When these cells are attached to the allergen, they break up and release potent chemicals such as histamines that cause local inflammation (redness, swelling and itching). This inflammation causes the various signs associated with an allergic reaction.
What are the symptoms of allergies in dogs?
The most common symptom associated with allergies is itching of the skin, either localized (in one area) or generalized (all over the body). The classic distribution pattern pruritis (itching) in these patients is the feet forearms, face and ears. This is usually manifested as an intense licking of the feet and forearms and scratching of the face and ears. Another group of symptoms that is not as common involves the respiratory system with coughing, sneezing, and/or wheezing. Sometimes, there may be runny discharge from eyes or nose. The third manifestation involves the digestive system resulting in vomiting and diarrhea.
How common are allergies in dogs?
Unfortunately, allergies are quite common in dogs of all breeds and backgrounds. Most allergies begin when the pet is between 1-3 years of age and typically progress and get worse as the pet ages.
Are allergies inherited?
Some allergies are inherited. The inherited trait is known as Atopy (see What is Inhalant Allergy or Atopy below).
What are the common allergy-causing substances (allergens)?
A very large number of substances can act as allergens. Most are proteins of insect, plant or animal origin, but small chemical molecules known as haptens can also cause allergy. Examples of common allergens are pollens, mold spores, dust mites, shed skin cells (similar to “pet allergies” in humans), insect proteins such as flea saliva, and some medications.
What are the different types of allergy?
There are several ways of classifying allergies. Some examples of classifications include:
Precipitating allergen - Flea Allergy
Route the allergen takes into the body - Inhalant Allergy, Skin Contact Allergy or Food Allergy
Time it takes for the immune reaction - Immediate-type Hypersensitivity, also called Anaphylaxis or Shock and Delayed-type Hypersensitivity
Type of immune reaction - Types I through IV Hypersensitivity
Clinical Signs - Allergic Dermatitis or Allergic Bronchitis
Inherited forms - Atopy or Seasonal Allergies
What is Contact Allergy?
Contact allergy is the least common type of allergy in dogs. It results from direct contact to allergens contained in flea collars, chemicals in the lawn or the grasses themselves and bedding, such as pyrethrins or wool. If the dog is allergic to these substances, there will be skin irritation and itching at the points of contact, usually the feet and stomach. Removal of the allergen (once it can be identified) often solves the problem. As well as shampoo therapy to dilute the allergen from the skin.