Dog allergies: why the symptom is rarely the cause

Your dog scratches himself raw, licks his paws sore, shakes his head — and nobody finds the trigger. Why the hunt for the one culprit so often fails, and which mistake in thinking follows most allergic dogs for years.

I know this phone call. “We have tried everything. Changed the food, three times. Cortisone helped, then it came back. The blood test says beef, chicken and house dust mite. And she still scratches her paws raw.”

Almost always the same mistake in thinking lies behind it — and it is an understandable one, because it sounds so logical: we look for the one trigger. The culprit. The single food you have to leave out for everything to be well.

But that is very rarely how an allergy in a dog works.

First of all: there is no such thing as “the” allergy

In veterinary medicine we essentially distinguish three forms, and at home they feel almost identical to you — the dog itches.

1. Flea saliva allergy. The most common and the most underestimated. A single flea bite is enough, and you do not have to find any fleas in the coat.
2. Atopic dermatitis. The reaction to environmental allergens — house dust mites, pollen, mould spores. Depending on the survey it affects around ten to fifteen per cent of dogs in Western countries, making it by far the most common true allergy.
3. Food allergy. The one everybody thinks of first — and the rarest of the three.

And now the point that makes the biggest difference in practice: These three do not exclude one another. A dog can have all three at once. That is exactly why leaving out a single food often achieves so little.

The mistake with the blood test

I am reluctant to be blunt here, but your money and your dog’s time are at stake: There is no reliable blood test, saliva test or hair test for food allergy.

These tests measure antibodies. An antibody says the body has been in contact with a substance — not that it reacts allergically to it. The common IgE blood tests do have usable specificity in dogs, but very low sensitivity: they miss a considerable proportion of affected animals. Both the American and the European specialist bodies for veterinary dermatology therefore name a single gold standard: the elimination diet.

If someone takes a hair sample from you and then sends a list of 40 intolerances, you are not holding a diagnosis. You are holding an invoice.

How an elimination diet really runs

The elimination diet is unspectacular, laborious and long. It is nevertheless the only way.

• Eight to twelve weeks of one single protein source your dog has never had before — or a hydrolysed food from the vet.
• Truly nothing else. No treat, no chew, no dental stick, no scraps from the table, no flavoured worming tablets. A single slip makes eight weeks worthless.
• Then the challenge. The old food is deliberately given again. If the itching returns, the diagnosis is confirmed. Without this step you know nothing for certain.

The most common reason an elimination diet “did not work”: it was stopped after three weeks, or a treat slipped in alongside after all.

The threshold principle — and why it explains everything

Now to the model that helps me most in practice and is at the same time recognised in conventional medicine: the itch threshold.

Picture a barrel. Every irritant fills it a little: the pollen in spring, the house dust mite in the sofa, the one flea bite from the meadow, the food, a dry skin barrier in winter, the house move, the new cat in the household, your own stress. As long as the barrel does not overflow, all is quiet. When it overflows, the dog scratches.

That explains three things owners regularly despair over:

• Why the same dog is free of symptoms in winter and not in May.
• Why removing a single trigger is sometimes enough and sometimes achieves nothing at all — it depends how full the barrel already was.
• Why it suddenly starts although “nothing at all” has changed.

For you that means: you do not have to find the one culprit. You have to lower the level. Every factor you take out gives some air — even if on its own it does not explain the allergy.

What is possible medically

I am a veterinarian, and I say it plainly: with a severely itching dog, medical treatment is not the second choice but the beginning. A dog that scratches himself raw at night needs relief first — and there are drugs today that work far more specifically than the cortisone of earlier decades.

The only approach that treats the cause itself rather than only the itching is immunotherapy for a proven environmental allergy: over months the body is gradually accustomed to the allergen. Depending on the source, success rates are around 60 to 70 per cent — not in every dog, but in many, and lastingly. It takes patience and belongs in experienced hands.

Which diagnostics your vet needs for this is their decision — not that of a test laboratory on the internet.

Where my perspective comes in

And here begins the part that usually has no room in a consultation because it takes time: when a dog has itched for years although everything has been treated, it is worth looking at the barrel — not only at the drop that makes it overflow.

I then look at things that on their own explain no allergy but together raise the level: digestion, and how steady it is through the day. The skin barrier, and whether it has any chance to recover at all. The stress level in the household — the human’s as much as the dog’s. I have seen a dog grow calmer as its human grew calmer far too often to put it down to coincidence. More on how I see this connection is in my article on holistic veterinary medicine.

This is no substitute for treatment. It is what runs alongside it — and it often decides whether the treatment holds or starts again from scratch every three months. How to learn to read your dog’s subtle signals in the first place I show in the course “Decoding the language of animals”. If your dog is restless and you are unsure whether itching, pain or something else lies behind it, you will also find help in When your dog shakes .

What I would like to leave you with

Your dog is not a puzzle you have to solve by guessing the right food. He is a system that is under strain in too many places at once.

Stop looking for the one culprit. Home emptying the barrel — a little in every place. That is less spectacular than a test with a long list. It just happens to work, unlike the test.