Many dog owners, at some point, will wonder whether their pet suffers with allergies. As the holistic approach to pet care becomes more popular, many owners are considering whether their pup’s diet is causing them issues. As a result, allergy testing for dogs is becoming more and more popular. Many at-home allergy test kits claim to diagnose your pet’s allergies from a hair or saliva sample… but is it really that simple? 

How do I know if my dog has allergies?

Skin allergies are one of the most common causes of itchy skin in dogs, alongside fleas and other parasites. Dogs can either be allergic to things in their environment, such as pollens, grasses, fleas and house dust mites, or to ingredients in their food. Most dogs with allergies will be allergic to more than one thing. 

The most common symptoms of allergies in dogs include:

  • Itchy skin
  • Sore skin or a rash
  • Fur loss
  • Pinkish saliva staining of the fur (from constant licking)
  • Recurring hot spots (acute moist dermatitis)
  • Ear infections

In the case of food allergies, you may also see gastrointestinal symptoms such as diarrhoea, sickness or excess gas. 

If you are seeing any of these signs, or you suspect that your dog has allergies, book an appointment with your vet. It’s important that they rule out other (potentially more serious) conditions that can cause similar symptoms. 

Do dog hair allergy tests work?

Many companies are now offering the convenience of sending a hair sample or saliva swab to a lab for allergy testing, for a relatively small fee. Seems too good to be true? Sadly, that’s because it is!

There is no scientific basis for dog hair allergy tests. In fact, one study in 2019 showed that hair and saliva tests failed to identify allergies in dogs. They sent ten fur and saliva samples from a known allergic dog, ten from a non-allergic dog and five fake samples (that were water and toy fur) to a lab. The range of results across each group was similar, and no different than you would expect from random chance. So, allergies detected were similar in allergic dogs, non-allergic dogs and toys! Also, the reproducibility of the results was poor. The study concluded that hair and saliva testing should not be used to diagnose allergies. Other studies have come to the same conclusion.

The moral of the story? Don’t waste your money! If you suspect your dog has allergies, seek advice from your vet.

How do you test for allergies in dogs?

Your vet will start by ruling out other conditions. This could involve trial treatment, blood tests (for example for some hormonal conditions) and /or skin biopsies. Diagnosing allergies is a process of elimination.

If your vet suspects environmental allergies, there are two options for finding out what they are allergic to:

  • A blood test or
  • Intradermal testing (injecting small amounts of allergen under the skin and watching for a reaction).

Your vet will normally only suggest these if your dog is going to be treated with immunotherapy. This means injecting small amounts of what they are allergic to under the skin, over a period of time, to desensitise them to the allergens. 

Since dogs usually have multiple allergies, it would be impossible to avoid them all. If you aren’t considering immunotherapy, then the medication options are the same, regardless of what your dog is allergic to.

If your vet suspects food allergies, there is no reliable test for this

Neither the blood test nor the intradermal testing are accurate for food allergies. The best way to test for a food allergy is by carrying out an elimination diet trial for 8 – 12 weeks. 

An elimination diet trial involves feeding a special veterinary prescription diet, which has been made so that your dog can’t react to it (the proteins are hydrolysed, or broken down). You would need to feed only this diet and water (no treats or human food) for at least 8 weeks. If your dog’s symptoms improve, your vet will then ask you to feed your dog their old diet again (this is called re-challenging). If their symptoms recur on the original diet, this confirms food allergies.

Once a food allergy has been diagnosed, your vet can help you to find out which foods your dog is allergic to, so you can find a diet that suits you and your pet long term. It’s important to note that your dog can develop new allergies with time, so if your dog’s symptoms recur, you should let your vet know.

Take home message

There is no evidence that allergy testing on dog hair or saliva is reliable. In fact, there are studies showing that they don’t work. Don’t waste your money! If you suspect your dog has an allergy, book a consult with your vet.

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