Allergy triggers in dogs: why is my dog really itching?

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Over the years at FendaF I have spoken to many people whose dogs scratch, lick their paws or struggle with recurring ear problems. One owner has already changed food three times; another has tried ten different shampoos. Eventually the whole story gets reduced to one sentence: “He must be allergic to something.” Perhaps he is. But to what, and how do we know?

For me, the most important question is still “but why?” Itching is a symptom, not a diagnosis. The skin can itch because of an allergy, parasites, bacterial infection, an overgrowth of yeast or several factors acting together. If we look only at the food bowl, we might miss the real cause. If we look only at the redness, we may overlook what keeps triggering the inflammation.

This article is not intended to label every medicine bad or blame every itch on food. Instead, let us look at what can cause allergies or aggravate an existing skin condition, what we can realistically change at home, and when more precise diagnosis is needed.

Why do some dogs develop allergies?

With allergies, the immune system reacts to a substance in a way that causes problems in the body. Canine atopic dermatitis is frequently associated with inherited predisposition, differences in the skin barrier and environmental allergens. That does not mean a particular breed is destined to become allergic, or that a puppy from healthy parents can never have allergies. It is nevertheless sensible to ask a breeder about skin disease, recurring ear infections and allergy treatment in parents and close relatives.

Holistic veterinarian Dr Edward Bassingthwaighte has described itchy dogs with red skin, inflamed ears and night-time scratching that keeps both dog and owner awake. His approach emphasises diet, environment, stress and the individual dog’s overall health. I relate to that view: a symptom does not exist independently of the rest of the dog. But calling every such case a single “dysregulated immune system” is not sufficiently precise to evaluate the individual patient.

Fleas and other parasites: do not skip this possibility

Flea allergy is a reaction to flea saliva. In a sensitised dog, even limited exposure can provoke severe itching, especially around the lower back, tail base and thighs. And no, you do not necessarily have to find a live flea in the coat for this to be possible. Other external parasites can also cause itching. Checking for fleas and mites belongs among the first steps, not something we think of after trying six different foods.

Choose a parasite control plan with your veterinarian, taking account of the dog’s health and actual exposure. No preventive product is entirely risk-free, but untreated parasites also carry risks. If several animals live in the home, all of them, and sometimes the environment, need to be considered.

Food may be the problem. But not always

Among FendaF customers are dogs whose itching, digestive complaints or coat problems improved noticeably after a food change. I have seen those changes myself, including after a switch to Winner Plus. I do not want to dismiss that experience. At the same time, improvement alone does not prove that the previous food caused an allergy: several things may have changed at once, and skin symptoms sometimes fluctuate naturally.

A food-responsive dog may react to a particular protein ingredient, although other food components can sometimes cause problems too. That does not mean all grains, carbohydrates or beef products cause allergies. Nor does a higher percentage of animal protein automatically make a food better for an allergic dog. Palatability, nutritional adequacy and the diagnostic usefulness of a diet are different questions.

When a food-related skin reaction is suspected, the most reliable approach is a properly conducted elimination diet followed by a controlled food challenge. The selected food is fed strictly for a sufficient period, with other foods, chews and flavoured supplements excluded. Evaluating skin signs can require eight to ten weeks or even longer. Some dogs improve sooner, but a trial that is too short can give a misleading answer. Switching recipes every day makes it impossible to tell reliably what the dog reacts to.

Some integrative veterinarians recommend feeding one food for at least 30 days to observe its real effect. I like this approach and often use or suggest it during ordinary food changes. A diagnostic elimination trial for suspected skin allergy, however, may need to last longer.

Pollen, dust mites and the home environment

Environmental allergens include dust mites, pollen and certain moulds. Some dogs worsen during a particular season; others have problems throughout the year. The timing of symptoms can offer valuable clues. Does paw licking increase after a long walk? Are the ears worse in spring? Does itching follow a bath with a new product, or the use of heavily fragranced household cleaners?

Practical steps are straightforward: wash bedding covers, reduce visible dust, choose fragrance-free cleaning products and, when appropriate, gently rinse or wipe paws and the underside after outdoor walks. The goal is not a sterile home. We are trying to reduce exposures that are actually relevant to this dog. Eliminating every airborne allergen is not realistic.

FendaF’s Health Corner also has a separate article on five possible sources of allergens in the home. Here our focus is how to distinguish the causes of itching.

Yeast and bacteria can complicate the picture

Red, warm skin with a characteristic odour, of the kind described by Dr Bassingthwaighte, often resembles a secondary infection too. Malassezia yeast can live on the skin without causing disease. Problems arise when it overgrows and the skin becomes inflamed. Bacterial skin infections can likewise make itching worse. These are not necessarily alternatives to allergy; they may occur alongside allergic skin disease.

That is why examining a skin sample or performing ear cytology can sometimes be a far more useful first step than buying another “allergy food”. If an infection needs treatment, a supplement or homemade rinse cannot replace appropriate care. And if the infection keeps returning, we need to ask what is making it recur.

Stress and skin: the link exists, but not everything is “just nerves”

Moving home, losing a family member or another pet, and constant excitement may affect a dog’s sleep, behaviour and scratching. Stress can intensify existing itching. But stress alone cannot diagnose an allergy, and inflammatory skin disease should not simply be explained away as an emotional issue.

Sometimes a simple diary gives the best information: where redness appeared, when licking happens, what the walk was like, what food and treats the dog ate and whether a new cleaning product was used. Patterns may emerge that one short veterinary appointment cannot reveal.

What about vaccines and allergy medicines?

I have spoken openly about Oscar’s health problems, including the improvement I noticed during a period when I did not vaccinate him. That is my real experience. Other aspects of Oscar’s life and health management changed during the same period, however, so it cannot prove that vaccines caused his skin problems. Vaccines can cause adverse effects, including allergic reactions, but an acute vaccine reaction is not the same thing as the development of chronic atopic dermatitis. I decide on vaccination needs and timing according to the individual dog’s health and infection risks, in discussion with a veterinarian.

I still believe it is important to look for the cause of itching while treating symptoms. But we need to be precise about medicines. Corticosteroids can relieve symptoms quickly, yet may have substantial side effects, particularly when used long term. Oclacitinib, known as Apoquel, acts on immune signalling and can increase the risk of infections in some dogs. European product information also advises monitoring for certain neoplastic conditions. This does not demonstrate that the immune system “never recovers” after stopping the medicine, although some integrative veterinarians have raised concerns. The balance of benefits and risks in long-term therapy depends on the dog’s condition, other illnesses and follow-up.

Integrative veterinary medicine also uses natural approaches, diets intended to support the skin and selected supplements. Some have biologically plausible mechanisms, some are supported mainly by clinical experience and others have weak evidence. That does not make them all pointless, but neither does it justify claiming that they always replace needed medical treatment. There is no convincing clinical evidence that homeopathy treats allergic skin disease in dogs.

How can we start helping an itchy dog?

I do not give identical advice for every itchy dog. One may need dietary changes, another proper parasite control, another treatment of a skin infection, and some need several approaches together. This can take longer than buying one jar. But at least we are following the right question instead of another guess, food bag or supplement tub.

Sources

• 2023 AAHA Management of Allergic Skin Diseases in Dogs and Cats Guidelines
• Merck Veterinary Manual: Atopic Dermatitis in Dogs
• Merck Veterinary Manual: Cutaneous Food Allergy
• European Commission: Apoquel product information
• FDA: Apoquel Safety-Related Labeling Changes