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Dog Allergies: Symptoms, Triggers and Treatment

7 min read
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Sponsored by PRO PLAN Vet Diets

Just like us, our dogs can suffer from certain allergies. Discover what the most common dog allergies are and how they’re diagnosed with Purina. 

Dog allergies are a reaction to foreign substances in your dog’s immune system – which is the same cause of allergic reactions in humans! Whereas it’s relatively simple to diagnose allergies in humans, it’s usually quite difficult for dogs as there are many different types of allergies and the symptoms often overlap. This makes it hard to understand which allergies they’re actually suffering from. 

If you suspect that your dog may be suffering from allergies, you may be wondering about the potential dog allergy symptoms and when to seek help from your vet. Keep reading to find out everything you need to know. 

Common symptoms of dog allergies 

There are various ways in which allergies can affect your dog. Depending on the cause, you may notice some of the following clinical signs:

  • Itchy skin – it’s one of the most common signs of dog allergies. Your dog will scratch, lick, or bite excessively, often leading to hair loss, redness, and skin irritation.
  • Paw chewing or licking – inflammation is especially common between the pads, causing dogs to lick or chew their paws excessively. This can lead to secondary infections in some cases.
  • Sneezing, coughing or runny nose – as with humans, dogs can get a runny nose, especially if they have an allergy to things such as pollen or dust mites.
  • Gastrointestinal problems –diarrhoea, frequent bowel movements, or occasionally vomiting. 
  • Skin rashes – you might notice hives on your dog’s skin. These will look like red patches or raised bumps that may be itchy or painful.

In an acute anaphylactic reaction, you may notice symptoms including wheezing, difficulty breathing, facial swelling, hives and vomiting. This is a separate condition to chronic dietary or environmental allergies, and requires urgent treatment. Most dogs with chronic allergies aren’t at high risk of anaphylaxis. 

What causes dog allergies? 

Allergies in dogs are brought on by an overactive immune response to substances that are normally harmless. Known as allergens, these substances can trigger certain reactions in sensitive dogs. Here are the most common causes of dog allergies:

  • Flea bites
  • Pollen from trees, weeds, and grass
  • Dust mites, mould spores, or dander
  • Foods such as beef, chicken, or dairy

Other causes of allergies include:

  • Certain fabrics, cleaning products, or grooming products
  • Medications
  • Cigarette smoke, perfumes, or aerosol sprays

Dog skin allergies 

Skin allergies, also known as allergic dermatitis, is one of the most common types of dog allergies. These are usually caused by reactions to flea bites or their surrounding environment such as pollen, dust, or mould. 

Flea allergies 

Fleas or a flea bite allergy is the most common skin disease in dogs. These dog allergies are a result of a reaction to flea saliva on your dog’s skin, and symptoms will vary from mild itching to a severe reaction when bitten. 

Usually these allergies will appear when they’re young (between 1-5 years old), but they can develop at any age. 

Dogs with flea allergies will usually have severely itchy skin. Itchiness is sometimes referred to by its medical term, ‘pruritus’. They may scratch, rub, chew, or lick their hair or skin, and this can sometimes result in trauma to the skin or introduction of a secondary infection. Additionally, other dog allergy symptoms may be present such as hair loss and scabbing, and flea dirt may be visible on the skin or in the coat too. 

Flea dirt can, however, often be difficult to spot, so the ‘wet paper’ test can help: rub your dog’s coat gently whilst they stand on a piece of damp paper. Any black flecks (flea dirt) that fall off the coat will stain the paper red (as flea dirt is dried blood). This can be a useful indicator of whether fleas are present or not. Bear in mind that even if your dog is treated monthly for fleas, they could still suffer from a flea allergy! Many flea treatments will only kill the flea once it has bitten your dog, and unfortunately this single bite is often enough to trigger an allergic reaction and itching in a sensitive dog. 

Environmental allergies 

Environmental dog allergies are usually caused by dust, pollen, or mould. This type is usually seasonal, so it will probably only appear at certain times of the year – dogs can suffer from hay fever so you may notice sneezing or irritation when the pollen count is high. Areas around the paws, ears, lower legs, muzzle, and groin are usually the most affected skin spots and your dog might have bald or sore patches from excessive itching. Sometimes, an environmental allergen can be resolved simply by ‘avoidance’ – for example, if you know your dog’s allergic symptoms appear worse on walks through particular fields with long grasses you may need to avoid this and use pavements at certain times of the year. 

Dog food allergies  

Contrary to popular belief, food allergies in dogs aren’t very common, and actually only make up about 10% of allergies or less in dogs. Most of what owners believe are ‘food allergies’ are actually intolerances. 

An intolerance differs to an allergy: an allergy involves the immune system, so the body must have been previously exposed to the ‘allergen’ (which is usually a harmless molecule). In comparison, an intolerance does not involve the immune system and can occur the first time a dog encounters that substance. An example would be a lactose intolerance: in this case, the dog would lack the enzymes needed to digest lactose, so if given some milk he or she may suffer from diarrhoea because of an inability to digest the ingredient. 

Although not always the case, an allergy tends to provoke a skin reaction, such as a swelling or itchiness, more commonly than a gastrointestinal problem like vomiting and/or diarrhoea, whereas an intolerance is more likely to result in gastrointestinal signs. 

If you think your dog might be sensitive to their regular food, you might try feeding them a diet that’s hypoallergenic such as PRO PLAN® VETERINARY DIETS HA Hypoallergenic Dry Dog Food.  

Acute allergic reactions 

Sometimes dog allergies can become severe and may result in anaphylactic shock. Most commonly these reactions are due to things like a bee sting or a wasp sting. 

Signs of anaphylactic shock can appear within minutes of exposure and may include difficulty breathing, drooling, vomiting, seizures, and sometimes even a loss of consciousness. If this does occur, you should contact your vet immediately. 

Diagnosing dog allergies 

If you suspect that your dog has an allergy you should take them to the vet as soon as possible. Your vet will be able to rule out any other possible causes and will run tests which can help to determine whether an allergy may be the cause of your pet’s symptoms or not.  

Food allergies are usually diagnosed through an elimination diet, which involves feeding a hydrolysed, hypoallergenic diet, and absolutely nothing else, for at least three weeks and looking for signs of improvement. Your vet may then choose to re-challenge your dog by adding in additional ingredients to observe for possible dog allergy symptoms and try to determine the cause(s) of the allergies, though this is not always the case. 

Flea bite allergies may be relatively straightforward to diagnose if fleas or flea dirt is visible in the dog’s coat, but bear in mind that in some cases the flea may already have been killed and have dropped off, so it is not always as easy as it sounds to determine the cause of the allergy. Your vet may be able to give you a treatment which kills the flea(s) very rapidly if they are still present. After this, you will need to ensure you treat your house as well as your pet, since 95% of fleas are in the environment and they could otherwise quickly hop back on to cause a problem again! 

Dog allergy treatment 

The treatment will often depend on your dog’s allergy, but will focus on removing the cause of the allergy where possible, and providing relief from the symptoms. A food allergy can be managed by removing the ingredient from your dog’s diet. 

A flea allergy may be helped by a ‘rapid kill’ flea treatment from your vet, and advice on how to treat your house and any other pets in contact with your dog. If your dog’s allergy symptoms are severe, your vet may also prescribe a medication to help deal with them, such as a medicated shampoo or cream for severe itching or an anti-inflammatory to help with any swelling or itchiness. 

If your dog is suffering from a severe allergic reaction you should take them to the vet immediately, as when left untreated anaphylactic shock can be fatal. 

Next, find out what to do if your dog has been stung by a bee or wasp with our easy guide. 

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