Diet and Itching: Is Scratching the only sign?

What causes itching (pruritus) in dogs?

Skin problems are one of the most common reasons for dogs to be presented at the vets, and itching is typically one of the clinical signs. There are a multitude of different skin conditions – and some problems unrelated to the skin – that can cause itching. Differentiating them can be a challenge for the veterinary team and a frustration for pet owners. 

Allergies are a major cause of itchy skin, and these can be grouped into the following main categories:

• Fleas (ectoparasites): Most dogs can have a flea infestation without exhibiting many signs, other than the occasional itch here and there. In dogs with flea bite hypersensitivity (sometimes called flea allergic dermatitis), an allergic reaction is mounted against flea saliva, and this can cause widespread skin inflammation and severe itching.

• Atopic dermatitis: These dogs have environmental allergies and react to things like household dust mites and pollens from grass and trees. 

• Food: Dogs with food allergies or intolerances can present with itchy skin. These are known as cutaneous adverse food reactions (CAFR).

N.B. these categories are not mutually exclusive and overlap between different types of allergies is common. 

The first thing to rule out is fleas. Safe and effective treatments are available for your pets, and the household environment. Dealing with the fleas in the environment (around the house) in addition to those on the dog is key, as this is where most of the flea material is found. In dogs with flea allergic dermatitis, diligent flea prevention for all relevant animals in the house will likely be advised going forward.

Atopic dermatitis and cutaneous adverse food reactions cannot be distinguished from the presenting signs alone, however there are some things that make one or the other more likely. For example, CAFR may be more common in young dogs (<1 year) or older dogs (>6 years); in those where the itching is non-seasonal; and in dogs that have concurrent gastrointestinal signs such as loose stools, gas or vomiting. 

Atopic dermatitis is what’s known as a diagnosis of exclusion

Atopic dermatitis is what’s known as a diagnosis of exclusion, meaning that other causes of the signs all need to be ruled out before a diagnosis can be made. In this case, that means ruling out CAFR.

What are the skin signs of allergies?

You may directly observe an increase in scratching, though sometimes the signs can be less obvious. These include:

• Foot chewing 

• Red/brown saliva staining on the feet 

• Red ears, frequent head shaking, rubbing ears on furniture

• Poor quality coat

• Scooting bottom along the ground

• Rolling around to scratch his/her back 

• Itchy eyes, tearing

• Recurrent ear and skin infections

• Change in the appearance or feel of the skin. You may notice a change in colour, scaling, greasiness, or small bumps

Using diet to reach a diagnosis

When it comes to differentiating atopic dermatitis from food allergies or intolerances, a vital part of the diagnostic process is something called an elimination diet trial. This involves feeding a specially prepared diet that it’s highly unlikely your pet is allergic to, to see how they respond. If the signs improve, a cutaneous adverse food reaction is possible, and the veterinary team may then ask you to feed your dog’s original diet to confirm that the signs return.

We’ve previously written an article about these specialised diets and how they work, Hypoallergenic Diets – What Are They and Are They All Equal? These are very different from some diets that are labelled as “hypoallergenic”, so it’s vital that you follow the instructions of your veterinary team very carefully when selecting a food and deciding how long to feed it for. During the diet trial, it’s important that your pet eats the recommended food and nothing else. You must assume that your pet is allergic to everything but the recommended food while this trial is taking place, so take care with kids dropping food, licking dirty plates in the dishwasher, flavoured toothpastes, supplements, treats etc.  You should ask your veterinary team about any medications or supplements before stopping them.

We understand that performing an elimination diet trial can be a real challenge in a busy household, but it’s the only way that food allergies and intolerances can be reliably diagnosed. If a cutaneous adverse food reaction is diagnosed, the treatment involves avoidance of the problem allergen. Approaches include continuing the diet that successfully improved the signs during the diet trial, considering an alternative “skin support” diet, or attempting to identify other foods that the dog can tolerate through trial and error. 

Diet for dogs with atopic dermatitis 

Unusual protein sources: Thus far, we have presented CAFR and atopic dermatitis as two separate conditions, but the reality is that they often overlap. In these dogs, a partial improvement may be seen during the elimination diet trial. The most commonly reported allergens in dogs are beef, chicken, dairy and wheat. It’s important to note that there’s nothing “wrong” with protein from these sources, they’re just very common and therefore most animals have been exposed and had the opportunity to develop an allergy to them. This is less likely to be the case for more unusual protein sources, so these will sometimes be included in diets for dogs with atopic dermatitis. 

High in excellent quality protein: 95% of a dog’s hair is protein, so it’s essential for a healthy coat. It’s also vital for skin repair and maintenance and for the formation of collagen, which is the principal component of a dog’s skin. Some amino acids (the building blocks of proteins) are more important than others when it comes to skin health, so the diet needs to be expertly formulated to have the right balance and quality of proteins, as well as an adequate quantity. 

High levels of long chain omega-3 and omega-6 fatty acids: omega-3 fatty acids (EPA and DHA) help to maximise the natural anti-inflammatory processes in the skin. Omega-6 fatty acids promote a healthy skin barrier and reduce water loss.

Other useful ingredients: diets specially designed for dogs with skin disease may also contain a blend of other skin supportive nutrients. This may include antioxidants, vitamin A and zinc. A compound called palmitoylethanolamide (PEA) may also help to reduce the severity of signs.

Your veterinary team may recommend a food that is specially formulated to support skin health. This is typically the most practical way to include the useful nutritional features discussed, while still ensuring that your pet’s diet is complete and balanced to support good overall health. 

Summary 

Allergies are not the only cause of itchy skin, though they are important. Other causes include parasites not mentioned here, infections, immune mediated diseases and even cancers, so it’s important to work with your vet to reach a diagnosis. Diet changes are a vital part of the diagnosis and management of allergic skin diseases in dogs. Choosing the right diet can be difficult, so it’s essential that you follow the advice of your veterinary team and let them know about any challenges you encounter. 

© Nestlé Purina Petcare 2025

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