Allergies

 

Allergies, also known as atopic disease, atopic dermatitis or allergic dermatitis are an exaggerated response from the body towards a particular substance, called an allergen.  Allergens are usually a type of protein found in foods, a pollen, bacteria or a mould. 

There are many different types of allergies in dogs and cats

  • flea
  • food
  • contact
  • atopy
  • bacterial hypersensitivity

Almost any environmental substance can act as an allergen and these allergens can be breathed in, eaten, touched or injected.  In some animals these allergens will cause symptoms of an allergy such as, for example, one or more of the following list:

  • Anaphylaxis – A very sudden and serious exaggerated allergic reaction causing swelling of some or all parts of the body.
  • Utricaria – a less severe sudden allergic reaction causing a rash like symptom for example hives. 
  • Itching/licking/chewing.
  • Coughing/sneezing/wheezing.
  • Diarrhoea/upset bowels

I have been told that my dog is atopic.  Is this the same as inhalant allergy?

Yes and no.  After flea allergy dermatitis (FAD) which is also known as flea hypersensitivity, atopy is the most common type of allergy in the dog.  It was once thought to be caused by an inhaled allergen to which the dog’s immune system overreacts and so the terms are often used interchangeably.  The cause of atopy is still unknown, it is probably due to contact of the allergic particles directly on the skin or mucous membranes.

What happens to the dog when this occurs?

Atopy in the dog is usually seen as severe generalised itching.  The dog chews, licks and scratches almost every area of the body, including the feet.  Saliva will stain light coloured hairs so that dogs that lick their feet excessively will have orange or reddish brown hair which is a physical signs your veterinary surgeon may notice.  The dog may also scratch and rub the face, particularly around the eyes and ears.  The axillae (armpits), groin and the inside of the thighs may also be affected.  Occasionally in the dog there will also be respiratory signs, usually in addition to the pruritus.

How do you diagnose this condition?

Diagnosis is not an easy process.  It is based on the presence of the signs discussed above and ruling out other causes of pruritus, e.g. parasites or skin infections etc.  The itching produced by grass pollen is similar to that produced by house dust mites.  Therefore your dog may be allergic to one or several different things at once, making diagnosis more difficult.

Careful history taking will narrow down the causes for example seasonality.  If symptoms only occur in the spring when a certain pollen is prevalent then this narrows suspicions.

I have been told my dog will have to have skin tests to make a diagnosis.  Is this true?

Skin tests may need to be performed to rule out other causes of itchiness, for example checking for infections and parasites.  However once other causes are rules out, in most cases the allergens can be diagnosed by either 

  • serological testing where a blood sample is taken from your pet and sent away to an external laboratory for testing.
  • Intradermal allergy testing which is a complicated procedure and you may have to be referred to a veterinary dermatologist
  • 4-6 week food exclusion trial.

Once the diagnosis has been made it is sometimes possible to de-sensitise the pet by using specific antigen injections which are made up according to the results of the skin tests.  The theory is that controlled injections of increasing amounts of specific allergen can re-programme the animal’s immune system to reduce its response.  For a proportion of animals this can result in significantly reduced severity of itching and in some it may be completely curative.

If this does not work, are there other forms of treatment that can be used?

Yes, frequently hyposensitisation is one of the last lines of treatment.  Anti-inflammatory drugs including corticosteroids and antihistamines will often bring the acute phase under control.  Other long term treatments are also available including Atopica®, Apoquel® and Cytopoint®.  In addition, the use of certain fatty acids, including evening primrose oil or fish oil can help.  However this is a non-specific approach that doesn’t treat the allergy, only reduces the resulting symptoms.

Many dogs are helped considerably by frequent bathing with special hypo-allergenic shampoos.  It has been demonstrated that some allergens are absorbed through the skin and the theory is that frequent bathing reduces the amount of antigen that the patient is exposed to by this route.

Please speak to one of our team to find the best investigations and treatments for your particular pet.

Why does my atopic dog smell?

When dogs scratch, sebum which is an oily material produced by the skin, often increases dramatically and is responsible for a musty odour.  Once the itching and scratching has been controlled usually the seborrhoea, due to the increased sebum, also clears up.

Another cause can be bacterial or fungal (yeast) infection.  This is due to the damage caused to the dog’s skin.  The ear canals are extensions of the skin.  These become badly infected and can be overlooked when the more obvious skin lesions are being treated.

 

Book an appointment to speak to one of our friendly team if you need further advice about your pet and their allergies.

 

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