What are allergies, and how do they affect dogs?
One of the most common conditions affecting dogs is allergy. In the allergic state, the dog’s immune system “overreacts” to foreign substances (allergens or antigens) to which it is exposed. These overreactions are manifested in three ways. The most common is itching of the skin, either localised (one area) or generalised (all over the dog). This commonly includes licking paws, and is regularly mistaken as a harmless habit. Ear infections are also a very common result of uncontrolled allergy. Other manifestations can involve the respiratory system and may result in coughing, sneezing, and/or wheezing. Sometimes, there may be an associated nasal or ocular (eye) discharge.
What do dogs become allergic to?
The most common type of allergy is the inhalant type, also known as atopy. Dogs may be allergic to all of the same inhaled allergens that affect humans. These include tree pollens (cedar, ash, oak, etc.), grass and weed pollens, moulds, mildew, and the house dust mite. Many of these allergies occur seasonally, such as the grass pollens. However, others are with us all the time, such as moulds, mildew, and house dust mites.
Most dogs who develop environmental allergy will show some signs before 3 years of age.
Most dogs who develop environmental allergy will show some signs before 3 years of age.
What happens when a dog inhales something to which it is allergic?
When humans inhale allergens, we express the allergy as respiratory problems. These include coughing, sneezing, a runny nose, and watery eyes. The dog’s reaction, however, usually produces generalised itching or tendency to easily develop rasjes or skin infections. It may chew, lick, or scratch any area of the body, including the feet. Chewing and scratching produce hair loss and inflamed areas of the skin. Saliva will stain light coloured hair, so dogs that lick excessively may have orange or reddish brown hair. This is often seen on the feet.
How do we find the cause of the allergy?
It is not possible simply by looking at a dog to know what it may be allergic to. Usually testing is necessary. Initially we will recommend food trialing to rule in or out food based allergy. A common response from pet owners is that "we haven't changed the diet so it can't be that". On the contrary, dogs can develop allergy to food they have been fed without problem for a long time. While environmental allergies are more common, it would be a shame to miss a food allergy, which is the easiest type to treat.
A novel protein trial involves feeding a single, new, protein source food for 8 weeks minimum. For example, if a dog has been fed chicken and beef as it's main protein sources each day, the aim would be to discontinue both of these proteins completely during the trial (including in treats and human scraps etc - ALL forms of food). The dog is then fed a brand new type of protein exclusively for 8 weeks minimum. At the end of the trial, the response is assessed and used to determine how much of a role food is playing in the allergy. If a dog has no improvement at all during a food trial, it is a sign that environmental allergy is the cause.
If you find it hard to source a novel protein food (such as if your dog has been fed a varied diet with many protein sources), the next best way to diet trial is called a hydrolysed diet, which works in a different way to a novel protein trial. Examples of food that are hydrolysed includes Hills z/d and Royal Canin hypoallergenic. The same guidelines apply. Stick to that food and ONLY that food for 8 weeks.
While food trialling is overwhelmingly the best first step, more dogs with signs of allergy are allergic to environmental allergens. If a dog's itchiness persists through the full term of a diet trial, environmental allergy is the likely cause. It is possible, through referral to a veterinary dermatologist, to have a test done to further assess for this. The test is similar to skin prick tests done on people to test for allergy. The results of this testing can either form the basis of a plan to avoid certain plants or grasses, or to have a custom made desensitisation therapy formulated by the dermatologist. This therapy (immunotherapy) aims to reduce a dog's exaggerated response to the specific allergens.
A novel protein trial involves feeding a single, new, protein source food for 8 weeks minimum. For example, if a dog has been fed chicken and beef as it's main protein sources each day, the aim would be to discontinue both of these proteins completely during the trial (including in treats and human scraps etc - ALL forms of food). The dog is then fed a brand new type of protein exclusively for 8 weeks minimum. At the end of the trial, the response is assessed and used to determine how much of a role food is playing in the allergy. If a dog has no improvement at all during a food trial, it is a sign that environmental allergy is the cause.
If you find it hard to source a novel protein food (such as if your dog has been fed a varied diet with many protein sources), the next best way to diet trial is called a hydrolysed diet, which works in a different way to a novel protein trial. Examples of food that are hydrolysed includes Hills z/d and Royal Canin hypoallergenic. The same guidelines apply. Stick to that food and ONLY that food for 8 weeks.
While food trialling is overwhelmingly the best first step, more dogs with signs of allergy are allergic to environmental allergens. If a dog's itchiness persists through the full term of a diet trial, environmental allergy is the likely cause. It is possible, through referral to a veterinary dermatologist, to have a test done to further assess for this. The test is similar to skin prick tests done on people to test for allergy. The results of this testing can either form the basis of a plan to avoid certain plants or grasses, or to have a custom made desensitisation therapy formulated by the dermatologist. This therapy (immunotherapy) aims to reduce a dog's exaggerated response to the specific allergens.
What is meant by “seasonal allergy” and “year round allergy”?
As the names imply, some dogs only have allergic reactions during specific periods of the year. Others will itch year round. A year round allergy occurs for two reasons. First, the allergen is present year round. This is the case for indoor dogs that are allergic to house dust mites, also known as “house dust”. Second, the dog is allergic to so many things that at least one of those allergens is present at all times.
My dog seemed to have a seasonal allergy for several years, and now it seems year round. Is that possible?
Not only is that possible, it is almost expected. As the dog ages, it usually becomes allergic to more and more things. After several years of acquiring new allergies, it reaches the point that it is constantly exposed to something to which it is allergic.
How is inhalant allergy treated?
Treatment depends largely on the length of the dog’s allergy season and involves a number of approaches:
- Avoidance of the allergen is the best and most effect treatment. See above for details on food trialling and skin prick testing.
- Rigorous control of any "secondary infections" including yeast and bacterial infections of the skin and ears. These infections are facilitated by the skin being in an allergic state.
- Year round protection from flea bite, which can greatly exacerbate itch levels in allergy prone dogs. Don't assume your dog is somehow immune to fleas because they've never had them
- Symptomatic control of itchiness. While we don't necessarily want to "paper over the cracks", making sure dogs are not constantly bothered by their itchiness is an important goal and has a large bearing on quality of life.
- Cytopoint injections are antibody therapies given by injection at the clinic. They have a very high likelihood of controlling itch quickly and a very low likelihood of side effects. We expect at least 1 month of itch control from each injection.
- Apoquel and cyclosporin are 2 oral medications that have been used to control allergic itchiness. They have a moderate incidence of side effects and a good likelihood of control of itchines
- Steroids like prednisolone are generally very good at controlling itch but also very predictable as far as causing short and longer term side effects.
- Anithistamines like Claratyne or Zyrtec are relatively safe and easy to source but have a low success rate
- Daily supplementation of omega 3 and 6 fatty acids may mildly reduce allergic signs over a long period of time
- Plain water rinsing of feet and other skin may reduce allergic flare after being in plant-rich environments
My dog has a terrible odour. Is that related?
There are two possible causes of odour associated with inhalant allergy. These dogs are very prone to ear infections because the ear canal is an extension of the skin. When it becomes inflamed, it is easily infected and this will smell it is likely to have seborrhoea.
Sebum is the oily material normally produced in the skin. When a dog scratches, sebum production increases dramatically. This produces a musty odour. A bath will remove the odour, but it is gone for only a few hours. The key to controlling seborrhoea is to stop the itching and scratching. In addition the sebum is a good medium in which bacteria can grow. This again results in an unpleasant smell.Text
Sebum is the oily material normally produced in the skin. When a dog scratches, sebum production increases dramatically. This produces a musty odour. A bath will remove the odour, but it is gone for only a few hours. The key to controlling seborrhoea is to stop the itching and scratching. In addition the sebum is a good medium in which bacteria can grow. This again results in an unpleasant smell.Text
Is there another disease that can be part of my dog’s problem
Yes. Skin infections (which themselves may increase itching) are common with atopy and may aggravate allergic conditions.