Food allergy in dogs: elimination diet and the right food

Nami at a few months old – shortly before her long itching phase.

In dogs, food allergies usually show up on the skin: itching on the paws, ears, belly and bottom, often with recurring ear infections. The only reliable way to identify one is an elimination diet lasting at least eight weeks, followed by a food challenge. The most common triggers are beef, dairy products, chicken and wheat.

With our Nami, it started when she was just under 5 months old. She was scratching constantly – paws, belly, behind the ears. Three vets found nothing conclusive. We were recommended a special food, small tin, one every day – in the end we'd spent a low three-figure sum on the vet practice brands, without any improvement. It was only when we switched to home cooking that things calmed down after a few weeks. Today she no longer scratches, her coat is shiny, and since then she hasn't had a single tick (no joke – before that, every summer was a disaster). If your dog has been licking their paws raw for weeks, has brown staining between their toes or is already on their second ear infection this quarter – they may be reacting to something in their food.

Food allergies are far from a fringe topic in our community. In dogs with chronic itching, a reaction to food is one of the more common causes – alongside environmental allergies, fleas, mites and skin infections. The good news: you can find out fairly reliably. The less good news: it takes patience and discipline.

In dogs, a food allergy rarely shows up in the stomach – unlike in humans. The skin is the main organ where you'll see it.

• itching, especially on the paws, armpits, groin, ears and around the bottom
• paw licking to the point of brownish-red discolouration (saliva oxidises)
• recurring ear infections, often on one side
• hot spots, i.e. inflamed, weeping patches
• chronically soft stools or a constant 4 to 6 poos a day
• wind and a rumbling tummy after eating

Important: all of this can also be caused by mites, fungi, atopy (environmental allergy) or fleas. Before you start an elimination diet, have your vet do a skin scraping and a blood test. Otherwise you'll spend weeks on a diet fighting a symptom whose cause lies elsewhere.

Interestingly, dogs usually don't react to “exotic” ingredients, but to what they've been eating for years. Constant exposure leads to sensitisation.

An analysis of all published cases arrives at this order: beef (a good third of the dogs), dairy products, chicken and wheat; less often lamb, soya, egg and others. Lamb used to be the insider tip for dogs with allergies – today it's found in many standard foods and can also trigger reactions. Which types of meat lend themselves to a diet is covered in our guide to which meat is best for dogs; whether grain really is the culprit is answered in do dogs need grain.

What many people underestimate: even a dry food “with salmon” often contains hidden chicken fat, hydrolysed chicken protein or egg powder. Read the whole ingredients list, not just the front of the pack.

This is the gold standard. No blood test for allergies comes anywhere close to being as reliable. For at least 8 weeks, you feed only one protein source that your dog has never eaten before – plus a carbohydrate source that's also new to them.

Popular combinations in German-speaking countries: horse with parsnip, kangaroo with sweet potato, ostrich with millet, goat with pumpkin. The alternative: a hydrolysed diet food from the vet – in these, the protein molecules are broken down so far that the immune system no longer recognises them as allergens. Not to every dog's taste, but a very good option for diagnosis.

Eight weeks means: 8 weeks without a single slip-up. No cow's ear from the father-in-law, no cheese rind from the neighbour's child, no other variety in between “because Otis loves it so much”. This is exactly where many attempts fail. Talk to everyone who sees your dog regularly – family, the dog boarding kennel, the dog training school.

Keeping a diary is a must: date, what was fed, itching on a scale of 0 to 10, stool quality, skin condition. After 8 weeks, you'll see from the trend what has happened.

This is where many people go wrong in their thinking. If the symptoms have gone after 8 weeks, you still don't know whether it was down to the food or whether it just happens to be a pollen-free summer. That's why you now deliberately reintroduce the old food. If the itching comes back within 1 to 14 days, the diagnosis is clear.

After that, you can challenge with individual ingredients – for example, 7 days of adding only beef, then a 14-day break, then 7 days of only chicken. That way you find out exactly what the problem is and what your dog tolerates. Time-consuming, yes. But at the end, you'll know precisely where you stand.

Oh, and one point that's often underestimated: patience. The skin has a memory. If your dog isn't itching less after 4 weeks, that doesn't mean the diet isn't working. Analyses show: after about 5 weeks, more than 80% of affected dogs are better, and after 8 weeks more than 90%. And if you give a cube of cheese on day 50, you'll effectively be starting again from zero.

A tip from our community: work out in advance what it will cost and buy a 4-week supply. If you go back to the counter halfway through, you're more prone to impulse buys.

If your dog has a confirmed allergy, you don't need horse fillet from Canada for the rest of their life. You now know which proteins work and which don't. Many dogs tolerate 2 to 3 protein sources without any problems, and you can rotate. When you do, switch to new foods slowly – how is explained in how to change your dog's food properly. What remains important: read the labels for every new product. “With venison” isn't enough information – check whether there's chicken in it too.

In the DoggoMeal app, you keep your food diary, tick off symptoms and have the 8-week plan in front of you – including a reminder that today is day 47 and you need to hold out for another two weeks. You'll also find a database of foods and their ingredients, so you can quickly spot pitfalls such as hidden chicken fat. Get the app.