The most common reason for dogs and cats to be brought into the vets is for skin problems – usually itching or soreness. These symptoms may be due to parasite infestations (especially fleas) or infections, but in many cases, an allergy, or allergic reaction is the underlying cause.
Don’t allergies cause runny noses and sneezing, like hay fever?
In humans, yes, but in dogs itching skin is much more common (although “allergic rhinitis”, a sort of dog hay fever, does occur occasionally). The common symptoms of an allergy are:
- Itching skin
- Redness of the skin
- Hair loss
- Often, there will be scabs or sores due to self-trauma as the dog scratches excessively
- Ear “infections” – the ear is lined with skin, and strangely is often the first site to show signs of an allergy!
What about food allergies?
Food allergies are exactly the same – signs of stomach upsets are unusual. In the vast majority of affected dogs, the symptoms are of skin itching etc.
So how do you tell what a dog is allergic to?
That’s always the problem – because all allergies in dogs usually present with exactly the same symptoms! The answer is that you can’t tell just be looking at them, you’ll have to make an appointment to see one of our vets for further tests.
How are allergies diagnosed by the vets?
Firstly, we try to rule out other possible causes of the itching, such as parasites or infection. We may look for flea dirt in the coat, or take skin scrapes or smears to check for mites, yeasts, and bacteria. Once these are ruled out, we can start looking for the cause of the allergic reaction that’s making your dog miserable.
Usually, we’ll ask you a lot of questions about the symptoms – when did they start, do they ever stop, what times of the year. This isn’t because we doubt your story, it’s because we’re trying to work out if there’s a pattern to the symptoms that may give us a clue as to what is triggering them. This is particularly important when dealing with allergies to plant pollens, for example, which are often very seasonal.
The next step varies, depending on whether there is anything obvious on the “history” you’ve given us. For example, if your dog always gets worse after being walked in a particular park or field, we may suggest that you avoid that area for a couple of weeks and see if things improve.
In most cases, however, we’ll move on to specific allergy tests. There are three primary ones we can do.
Blood tests for IgE are a simple option – a blood sample is taken and sent away to a lab which will test for chemicals called “immunoglobulin E”, or IgE. These are a type of antibody, made by the dog’s immune system to fight disease; allergic dogs, however, may make versions of IgE that respond to pollen, or dust mites, or whatever it may be. By looking for the levels of these specific types of the chemical, we can see if the dog is likely to be allergic to that particular substance. Although this test is very simple, some allergic dogs show up as falsely normal on the test, and other normal dogs may show up as falsely positive, so the results have to be interpreted with care.
A more accurate test is the Intradermal Allergen Test. This is the “gold standard” in diagnosing most allergies, but is difficult, expensive, and is a little riskier, so is generally only carried out by specialist veterinary dermatologists. The dog’s hair is clipped on one side of their body, and tiny amounts of lots of different possible allergic triggers are injected into the skin. Then, the reactions to these injections are measured – if the dog is truly allergic to one of the substances, their skin will react around the site of that injection.
Unfortunately, neither of these tests are very useful for food allergies, so if we think that’s what is wrong with your dog, we will instead do a Food Exclusion Trial. This involves placing the dog on a diet consisting of either foodstuffs they have never eaten before, or a commercial hydrolysed diet (where the food has been processed to prevent the dog reacting to it). They must eat this food ONLY, and nothing else (no treats, no snacks etc.) for about eight weeks. If the dog is allergic to something in their diet, the symptoms will then resolve. Once that has occurred, single components of their normal food (e.g. beef, wheat, chicken etc.) are gradually reintroduced; once the symptoms recur, the last ingredient added back in is the culprit.
It all sounds rather long-winded – isn’t there a simpler option?
If you want to find out what is causing your dog’s allergy, no – there’s no other reliable way. However, we can usually still treat the allergy even if we don’t know exactly what it is!
Can dogs have multiple allergies at the same time?
Yes, unfortunately they can. That is the hallmark of a disease called Atopic Dermatitis, which can be quite tricky to manage.
If you think your dog’s allergic to something, make an appointment for them to see one of our vets!