Scratching The Itch: Dog Allergies

Dog allergies, also known as allergic dermatitis, occur when a dog’s immune system overreacts to a normally harmless substance. Instead of ignoring it, the hypersensitive immune system flags the substance as a threat.

When the body comes into contact with the allergen, it triggers an inflammatory response. These reactions most commonly affect the skin and ears, leading to itching, licking, inflammation, and often secondary infections. Allergic reactions can also affect the gastrointestinal tract, causing symptoms such as vomiting and diarrhea, and the respiratory system.

With repeated exposure that is left untreated, this inflammation becomes chronic. It eventually breaks down the skin’s natural protective barrier and causes the skin to thicken, leaving the dog highly vulnerable to painful secondary infections and making healing much more difficult.

Why Do Dogs Get Allergies?

The reason why some pets get allergies is complex and involves a combination of factors, such as:

Genetics

Certain breeds are more likely to develop allergies, suggesting a hereditary link that is passed down through generations.

Sensitive Immune System

An overly reactive immune response that misidentifies normal triggers as threats.

Compromised Skin Barrier

In dogs with allergic dermatitis, the skin’s protective outer layer has microscopic “gaps”. This allows environmental triggers to penetrate the skin more easily.

Allergen Contact

Direct exposure to specific allergens that trigger the reaction. Typically, the first exposure doesn’t cause symptoms, but instead, the immune system misidentifies the substance as a threat and produces antibodies against it. When contact occurs again, these antibodies are ready to “fight” and trigger the inflammatory response.

Types of Dog Allergies

Environmental

Environmental allergies are triggered by substances in your dog’s surroundings, such as grass/plant pollen, dust mites, mould spores and dander.
These allergens can be seasonal (worse in spring or summer) or year-round. Dogs with environmental allergies often start showing signs between 1 and 3 years of age.

Food

Food allergies are less common than environmental allergies, but can cause similar symptoms. They occur when a dog reacts to a specific protein or ingredient in their diet.
Beef, dairy products, chicken and lamb account for more than 70% of food allergies. Soy, wheat, corn, and egg are also known allergens.
Unlike environmental allergies, food allergies are non-seasonal and may also cause gastrointestinal signs such as vomiting or diarrhea.
Diagnosis typically requires a strict elimination diet trial to find the ingredient causing the allergy.

Flea Allergy Dermatitis

Some dogs are extremely sensitive to flea saliva, and even a single flea bite can trigger intense itching. These cases can be difficult to diagnose because the cause may not be evident, and fleas are often not visible.
Diagnosis is often based on the history and presenting issues. Consistent flea prevention is critical for these dogs.

Contact

Contact allergies are similar to environmental allergies and occur when a dog’s skin reacts to something it physically touches.
Common triggers include certain shampoos, topical medications, lawn chemicals, floor cleaners, and laundry detergents. Dogs can also react to specific fabrics, plastics, stainless steel food bowls, or the sap and oils of certain grasses and plants.
While contact allergies are less common, they can cause significant localised inflammation.

What Are The Symptoms?

While itching (pruritus) is the most noticeable sign, allergic dogs may show a range of symptoms, including:

• Excessive scratching, licking, or chewing
• Paw licking (often leading to stained fur)
• Fur loss
• Red, inflamed skin
• Face rubbing & scooting
• Thickened or darkened skin over time
• Recurrent ear and skin infections

Complete the online quiz about your dog and their behaviours to see if they’re showing signs of allergic itch. You’ll get the results in a personalised report that you can share with your veterinarian.

How Are Dog Allergies Diagnosed?

To diagnose the allergy and identify the specific allergen, a veterinarian will typically review the dog’s medical history, assess the symptoms, and perform a thorough physical examination. The location of the dermatitis, symptoms and when flare-ups occur can provide clues to the underlying cause.
However, pinpointing the exact allergen can be challenging and not always successful.

If there is an active skin flare-up, a skin scraping can be examined under a microscope to check for parasites, bacteria, or fungi. Additionally, the success (or lack) of an elimination diet trial plays a crucial role in the diagnostic process.

For severe, unresponsive, or complicated allergies, a referral to a veterinary dermatologist may be recommended. Much like humans, dogs can undergo ‘Intradermal Allergy Testing’.

This procedure involves injecting tiny amounts of common allergens just under the skin to monitor for an allergic reaction

What Are The Treatments?

Managing canine allergies requires identifying the type of allergy, such as environmental or food, and ideally avoiding the allergen altogether. Sometimes, completely eliminating exposure is unrealistic or impossible.

Because of this, effective allergy management usually requires a multimodal approach. The ideal treatment plan will depend entirely on the underlying cause, the severity of the symptoms, and your dog’s overall health.

Commonly prescribed treatments include:

Cytopoint

Cytopoint is a monoclonal antibody injection that targets and neutralises the specific protein responsible for itching in dogs.

Administered by a veterinarian as needed, typically every four to eight weeks, it is highly regarded because it stops the itch without causing broad immune suppression.

It has minimal side effects and is safe for dogs of all ages, from puppies to seniors. Furthermore, many owners prefer a single, long-acting injection over the hassle of administering daily medication at home.

Learn more here: Cytopoint Brochure

Apoquel

Apoquel is a daily oral medication that targets and blocks the specific pathways responsible for both itching and skin inflammation. It works incredibly fast, providing relief within just 4-24 hours after the first dose.

Apoquel is given daily as either a tablet or a beef-flavoured chew.

Whether a patient is better suited to Cytopoint or Apoquel depends on a variety of factors, and a veterinarian can help decide the best option to trial.

Learn more here: Apoquel Brochure

Corticosteroids (Steroids)

Corticosteroids are powerful anti-inflammatory medications often used as short-term treatments to control acute or severe allergy flare-ups. Steroids provide rapid, highly effective relief and are a very cost-effective treatment option.

Unfortunately, steroids carry a high risk of side effects, particularly with prolonged use. Short-term effects often include increased thirst, frequent urination, and weight gain. Long-term risks are more serious and include immune suppression, liver issues, and an increased risk of developing diabetes.

Because of these potential complications, steroids are typically reserved for short-term relief or carefully managed, specific cases.

Topical Therapies

Topical treatments are valuable for mild cases, managing localised flare-ups or as part of a broader management plan.

Options include:

• Medicated shampoos with antibacterial and/or antifungal properties, such as Malaseb and Pyohex, to treat flare-ups. Malaseb EVO can be used as a gentler maintenance shampoo while still providing antibacterial and antifungal treatment
• Aloveen oatmeal shampoo and leave-on conditioners for soothing, providing hydration and helping to repair the skin barrier
• Sprays or creams with corticosteroids to provide local steroid benefit with reduced systemic side effects
• ‘Pulse therapy’ for recurrent ear infections caused by allergic dermatitis. This requires administering ear medication (usually topical corticosteroids, antifungals, and/or an ear cleaner) on a fixed, recurring schedule. The goal is preventative treatment to keep flare-ups at bay

Hydrolysed Diet

If a food allergy is suspected, a prescription hydrolysed diet may be recommended. These diets require strict adherence for at least 6 to 8 weeks, during which your dog may have absolutely no other food, treats, or flavoured medications.

Veterinary diets such as Hill’s Prescription Diet z/d and Royal Canin Hypoallergenic contain hydrolysed protein, which means the protein molecules have been “smashed” into tiny fragments. These particles are so small that they essentially slip under the radar of the immune system, preventing an allergic or inflammatory response, even if the dog was originally sensitive to the source protein.

If an improvement is noted during the trial period, these diets can be safely continued long-term. Alternatively, trials of novel protein diets may be initiated to help pinpoint which proteins are responsible for the allergy.

Novel Protein Diet

Following a successful elimination diet trial, novel proteins can be introduced one at a time while the patient is closely monitored for any flare-ups or returning symptoms.

This approach introduces a single, intact, high-quality protein source that is entirely new (novel) to the dog’s immune system. 

Depending on what the dog has eaten before, novel proteins typically include kangaroo, crocodile, venison, duck, turkey, wild boar, or goat. Prime100 varieties are the most commonly recommended single-source, novel-protein diets.

If they remain completely symptom-free after a 6-8 week trial of a specific novel protein, another protein can be introduced to safely expand their permanent diet.

Hydrolysed Novel Protein Diet

Royal Canin Anallergenic takes the process a step further by using a novel protein source and hydrolysing it. The protein is broken down to the amino acid level and fragmented so thoroughly that the dog’s immune system cannot recognise it, leaving virtually no intact allergens to trigger a reaction.

It is typically reserved for dogs with immune systems so sensitive that standard hydrolysed diets aren’t enough to manage their symptoms.

Skin Support Diets

For dogs suffering from environmental allergies, specialised skin-support diets can play a vital role in managing chronic allergic skin disease.

These therapeutic diets are formulated with enriched levels of omega-3 and omega-6 fatty acids to actively reduce tissue inflammation and strengthen the skin’s natural moisture barrier. They also contain targeted antioxidants and nutrients to support immune balance and promote a healthy coat.

Prescription options such as Hill’s Prescription Diet Derm Complete and Royal Canin Skintopic are specifically designed to help manage a dog’s reactivity to environmental triggers over time, significantly lessening the severity of itching, scratching, and seasonal flare-ups.

Allergy Vaccines

After successfully identifying the specific allergen and depending on the type, a veterinary dermatologist can formulate an Allergen-Specific Immunotherapy (ASIT) regimen.

This treatment involves gradually exposing the dog to increasing amounts of the allergen, allowing their immune system to build a tolerance over time. Notably, immunotherapy is the only long-term management option that can reduce or completely eliminate the need for lifelong allergy medications.

While highly effective for many dogs, ASIT requires a significant commitment. It involves frequent injections and can take 6 to 12 months to achieve noticeable results. Some patients can be weaned off slowly after 2 years, whereas others need ongoing treatment.