What are allergies and how do they affect dogs?
Allergic reactions are very common in dogs and are fully described in a separate fact sheet on Allergies and Hypersensitivities.
Is there more than one type of allergy?
Yes, there are at least five common types of allergy in the dog:
e) bacterial hypersensitivity
I have been told that my dog is atopic. Is this the same as inhalant allergy?
Yes. After flea allergy dermatitis (FAD) or flea hypersenitivity, atopy is the most common type of allergy in the dog. It is caused by an inhaled allergen to which the dog’s immune system over reacts.
What sort of things are inhaled that cause it?
There are a whole variety of allergens which can produce atopy. These are very similar to some of the things causing hay fever or human asthma.
When the affected individual inhales dust, pollens or moulds, for example, the allergic response occurs.
What happens to the dog when this occurs?
Atopy in the dog is usually seen as severe generalised itching. Your 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. 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.
In humans inhaled allergens cause respiratory problems, hay fever or asthma. Occasionally in the dog there will also be respiratory signs, usually in addition to the pruritis.
How do you find the cause of my dog’s inhalant allergy?
Diagnosis is not easy. It is based on the presence of the signs discussed above and ruling out other causes of pruritis, e.g. fleas. However the itching produced by grass pollen is the same as that produced by house dust mites. In other words your dog may be allergic to several different things with the end result being the same, i.e. he is scratching himself to pieces.
Careful history taking will narrow down the causes. For example, if it only occurs in the spring when certain pollen is prevalent this narrows the field of investigation.
I understand my dog will have to have skin tests to make a diagnosis. Is this true?
In around 80% of cases diagnosis can be confirmed by intra dermal allergy testing. This is a complicated procedure and you may have to be referred to a veterinary dermatologist. Once the diagnosis has been made it is often possible to desensitise the dog. This involves the use of specific antigen injections which are made up according to the results of the skin tests. The theory is that the controlled injections of increasing amounts of the allergen reprogramme the dog’s immune system to reduce the response. For most dogs hypersensitisation results 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 hyporsensitisation is one of the last lines of treatment Anti-inflammatory drugs including corticosteroids and antihistamines will often bring the acute phase under control. In addition the use of certain fatty acids, e.g. Evening Primrose Oil, does help. However this is a non-specific approach that doesn’t treat the allergy, only the result, i.e. the pruritis.
My friend’s dog has an atopy and seems to be helped by regular shampooing. Can I try this?
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.
Some of the special shampoos incorporate fatty acids which may also be absorbed through the skin and so help to reduce itching.
Antibiotics may also help particularly if the dog has scratched to such an extent that there is a secondary bacterial infection.
My dog only seems to itch in the spring and I have been told she has a seasonal allergy. What does this mean?
Probably she is allergic to a particular type of pollen that is only produced during a specific period of the year, e.g. in spring. Some atopic dogs will have an all year problem, in other words it is not seasonal. This means the allergen is present throughout the year and in the case of indoor dogs a very common cause is the house dust mite.
Another explanation may be that the dog has developed separate hypersensitivities allergies to so many different things that at least one of those is present at any one time.
My dog has a grass allergy each year. Does that mean it should not walk on grass?
No. So-called grass allergies are more correctly grass pollen allergies. Closely cut grass with no seeding heads will not cause problems. However do remember the pollen is airborne and cutting your own grass will have little effect if you live next door to a flowering meadow.
Are there any other conditions connected with atopy that I should know about?
Yes. Some dogs with atopy also appear to be hypothyroid, in other words the thyroid gland is not producing sufficient thyroid hormone. This in turn affects the skin and may aggravate allergic conditions.
If you have any concerns in this direction, there are blood tests which will be undertaken.
When my dog is worst affected with her atopy she seems to have a terrible 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 infection due to the damage caused to the dog’s skin and also sometimes, since the ears and ear canals are extensions of the skin, these become badly infected and are overlooked while the more obvious skin lesions are being treated.