Food allergies and intolerances in dogs can be frustrating for owners and uncomfortable for the animals themselves. The signs are often subtle at first, such as occasional scratching or mild digestive upset, but they can progress into persistent itching, ear infections, chronic diarrhoea or even behavioural changes. Understanding how to identify the cause and create what's known as an elimination diet is key to restoring a dog’s wellbeing and preventing long-term health issues.

The first step is recognising the difference between an allergy and an intolerance. An allergy involves the immune system reacting to a specific protein, triggering inflammation and symptoms that can affect the skin, gut or both. An intolerance does not involve the immune system but still causes adverse reactions, often through difficulty digesting certain ingredients. In both cases, the signs can overlap and be difficult to distinguish, so it's essential to take a structured approach.

How to do it

Identifying the trigger begins with observation. Keep a detailed record of the dog’s diet, including every treat, chew and supplement, alongside any symptoms – and don't forget to write the exact time next to everything. This log helps to spot patterns, such as flare-ups after eating chicken or digestive upset following dairy. It is important to remember that reactions can be delayed, sometimes appearing hours or even days after the food is eaten, which can make the process more complex... but recording it all is the first step, and it's hugely helpful.

Now is the time to get input from the vet. They can often spot the patterns in your record, rule out other causes such as parasites or infections, and guide the process. While blood and saliva tests for food allergies are available, they are not always reliable in dogs, so dietary trials remain the gold standard. This involves feeding a simplified diet that removes all potential triggers for a set period, usually between six and eight weeks.

The vet can advise you on the elimination diet, and it will be based on a novel protein and carbohydrate source that the dog has never eaten before. For example, if the dog’s usual diet includes chicken and rice, the trial might use venison and sweet potato. Commercial veterinary diets are available for this purpose, but home-prepared options can also work if they are nutritionally balanced. It is vital that no other foods are given during the trial, including flavoured medications, table scraps or treats, as even small amounts of the offending ingredient can cause a reaction.

During the elimination phase, symptoms should be monitored closely. Improvement may be gradual, particularly with skin issues, as it can take weeks for inflammation to subside. If the dog’s condition improves significantly, the next step is the challenge phase, where the suspected trigger is reintroduced in a controlled way. If symptoms return within a few days, the link is confirmed and the ingredient should be permanently avoided. If symptoms don't return, then that ingredient might not have been the problem, and you should then rmeove that one and try the next suspect.

Some dogs have multiple sensitivities, which means you might need to repeat the process with different ingredients. In these cases, you really have to be patient and precise. It will be tempting to rush the process, but incomplete trials or accidental exposure can lead to inconclusive results and you'll have to start again... which prolongs the dog’s discomfort.

Once the triggers are identified, the long-term diet can be planned in discussion with your vet. This may involve continuing with the novel protein diet, switching to a hydrolysed protein diet where the proteins are broken down to reduce immune reactions, or carefully selecting commercial foods that avoid the problem ingredients. Owners should also be aware of hidden sources of allergens, such as in treats, dental chews or supplements.

Managing a dog with food allergies or intolerances is not just about avoiding the trigger. It's also about ensuring the diet remains balanced and meets the dog’s nutritional needs. Consulting a vet or a qualified canine nutritionist can help to prevent deficiencies, particularly if the diet is home-prepared. Regular check-ups are important to monitor the dog’s condition and adjust the diet if necessary.

In addition to dietary management, supportive care can help to relieve symptoms during the elimination diet. Medicated shampoos, omega-3 supplements and anti-itch treatments prescribed by a vet can improve comfort while the underlying cause is addressed. However, these should not replace the elimination trial, as they do not resolve the root problem.

For owners, the process can be demanding, requiring strict control over everything the dog eats and careful record-keeping. But the reward is a healthier, happier dog with fewer flare-ups and a better quality of life. Many owners also find that the process deepens their understanding of canine nutrition and strengthens the bond with their pet.

In the end, identifying food triggers and creating an effective elimination diet is a methodical but highly effective way to manage allergies and intolerances in dogs. With patience, precision and professional guidance, it is possible to pinpoint the cause, remove it from the diet and restore the dog’s comfort and health. The effort invested in these early stages pays off in the long term, allowing dogs to thrive without the constant burden of allergic or intolerant reactions.