Veterinary prescription diets can be utilised to assist with the management of a variety of conditions. If your dog suffers from chronic food allergies, your vet may advise you to transition them onto a Veterinary prescription diet as a long-term control method. You may be wondering if this diet is essential and what it actually entails? This article will aim to explain how prescription foods such as ‘hydrolysed’ diets work and where they play a role.  

What is a food allergy?

If your dog has a food allergy, they will experience an immune-mediated reaction to a food component (either a single component or multiple ingredients). In most patients, the food component is a protein source. Published literature revealed that 65% of reactions in dogs are from beef, wheat or dairy products, whereas 25% are to lamb, soy, egg or chicken (Roudebush et al, 2000). Interestingly in felines, 90% of food allergies are associated with fish, dairy or beef products. Furthermore, there is a difference between food ‘allergies’ and food ‘intolerances’. The clinical presentation can be very similar, however, with a food intolerance the body doesn’t experience an immune-mediated reaction. 

Below lists some conditions which may result in your dog developing a food allergy (this list is not exhaustive):

Canine atopic dermatitis (CAD) 

This is a very common disease presented to vets worldwide. But it is still one of the most challenging (and sometimes frustrating) conditions to successfully manage. Many breeds can be genetically predisposed to CAD, such as French Bulldogs and West Highland White Terriers. Food allergies are often over-represented in younger animals, less than 1 year of age. CAD can be triggered by three main allergy categories: flea/parasitic hypersensitivities, environmental allergens, e.g. house dust mites, or food allergens. Some canine patients can suffer from more than one of these categories, which is why CAD can be referred to as a multifactorial disease process. A true food allergy is quite uncommon and therefore by altering your dog’s diet alone may not be enough to control the underlying allergy issue. 

Inflammatory bowel disease (IBD).

The abnormal inflammation in the bowel can cause the immune system to become hypersensitive, resulting in an allergic or other immune-mediated response. We’re not always sure which of the two conditions comes first – a real chicken and egg situation.

Exocrine pancreatic insufficiency (EPI). 

These dogs do not produce digestive enzymes to break down food, so providing a hydrolysed diet with easily digestible proteins can help to provide adequate nutrition. 

What are the clinical signs?

Below is a list of the most common clinical signs your dog may display if they are experiencing a food allergy (this list is not exhaustive):

  • Generalised pruritus (itchiness) usually of the tummy, face and feet.
  • Ear scratching and head shaking – this is often associated with chronic ear inflammation or irritation.
  • Excessive licking, particularly of the feet.
  • Gastrointestinal signs – e.g. diarrhoea and/or vomiting, noisy gut sounds, weight loss. 

Contact your Vet if you notice any of the above clinical signs. Your Vet will examine your dog and then will discuss the diagnostic and management options available.

What prescription diets for allergies are available?

There are a variety of branded Veterinary prescription diets for allergies available and they can vary in their quality and efficacy. Protein is perhaps the most vital component to any diet and it allows your dog’s body to function properly by supporting immune function, hormone production and maintaining tissues. As noted earlier, it is often the protein component which initiates an allergic response. Below summarises two types of prescription diets:

  • Your vet may advise that you transition your dog onto a hydrolysed protein diet. But what does the term ‘hydrolysed’ actually mean? In summary, hydrolysed diets are designed in very strict ways to reduce or eliminate their allergic potential. To simplify it, the hydrolysing method involves a process where special enzymes are used to break down protein into really small components called amino acids and peptides. Now for the even cleverer part! As the protein components are now much smaller, your dog’s immune system becomes tricked as their body stops identifying them as proteins. As a result, your dog no longer exhibits an allergic reaction (or at least this is the ultimate aim). Hydrolysed protein diets can be used in any age group.
  • Novel protein diet – these foods include alternative protein sources such as rabbit, venison, fish or kangaroo (it is important to ensure that your dog has not been exposed to these novel proteins before proceeding with this diet). Novel protein diets are not always suitable for younger animals during their development phase.

Are these diets always successful?

Simply, the answer is no! As mentioned earlier, dog allergic conditions may be triggered by multiple factors and, therefore, a diet alone may not be enough to control clinical signs. Your vet may advise an exclusive dietary trial for 6-12 weeks either via a home cooked method or a prescription diet. 

In addition, prescription diets have a better chance of working if they remain ‘exclusive’ and this is where owner compliance plays an important factor. This means that you should not feed your dog anything else. For example, if you feed your dog a hydrolysed prescription diet, but intermittently feed them non-hydrolysed treats or human food scraps, it will be extremely difficult to assess the true efficacy of the prescription diet. 

Not only do prescription diets aim to control and eliminate clinical signs, but they are also designed to provide your dog with balanced nutrition and all the vitamins and minerals they require to sustain good health. Working in a small animal general practice, I frequently come across owners who selectively create their own home-cooked allergy diet for their dog, however, I experience frequent concerns that these diets are not correctly balanced to meet their dog’s nutritional needs, so please discuss this with your vet first.

Other factors to also consider are medications as some tablets are coated in meat derivatives to add palatability!


To conclude, Veterinary prescription diets can play a role in the management of complex allergic conditions in dogs. Vets typically prescribe and advise these cleverly designed diets in specific canine individuals as a short or long term control method. It is advised to seek Veterinary advice to help to support you in selecting the right one for your dog.

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