Allergies in in dogs

Heather Giles

Allergies in dogs are very common and most often than not manifest themselves in the skin – itching or in the digestive system – diarrhoea.  Allergies can be very hard to treat as it can be difficult to identify the allergen and most conventional treatments only tackle the symptoms of the allergy ie reduce itching or inflammation.

1. What is an allergy?

“An allergy is a state of over-reactivity or hypersensitivity of the immune system to a particular substance called an allergen. Most allergens are proteins from plants, insects, animals, or foods.”

Exposure to the allergen, often over a long period of time, sensitises the immune system so that further exposure to the allergen causes an over-reaction.  Normally, the immune system helps protect your dog from disease however with allergies, the immune response is actually harmful to your dog’s body.

The immune reaction in an allergy is quite complex.  Protein molecules combine with antibodies in the blood and then attach a ‘mast’ cell, found in tissues throughout the body.  These mast cells then release chemicals such as histamines which cause local inflammation such as swelling and itching.  This inflammation causes the various signs associated with an allergic reaction.

2. What are the common symptoms of allergies in a dog?

Symptoms include:

• Itchy skin – localised or generalised
• Respiratory – coughing, sneezing, runny discharge from eyes/nose
• Digestive – diarrhoea or vomiting

Unfortunately, allergies are relatively common in dogs, appearing mostly in dogs over six months with most affected dogs being over two years old.

3. Nurture or Nature?

It’s believed some allergies are inherited and some breeds are more prone than others – for example, atopic dermatitis which is very common in West Highland White terriers.

Useful reading: 

- A guide to supplements for the skin

- Common Canine Digestive Problems

4. What are the most common allergens?

Most of the large number of allergens are proteins of insect, plant or animal origin, however, small chemical proteins can also cause allergy.  Examples of common allergens are:

• Pollens
• Mould spores
• Dust mites
• Insect proteins (such as flea saliva
• Some medications

5. What are the different types of allergies?

There are several ways of classifying allergies:

• Allergen – flea allergy, food allergy
• Route the allergen takes into the body – inhaled, contact (skin) or ingested (food)
• Time taken for the immune reaction – immediate type (anaphylaxis) or delayed type
• Clinical signs – allergic dermatitis or allergic bronchitis
• Inherited forms – atopy or seasonal allergies

6. How can allergies be treated?

Flea/insect bite allergy
Strict flea control is necessary otherwise an affected dog can react with severe itching leading to bacterial infection where the skin is broken.  If insect control is not possible or where the reaction has resulted in severe itching, a vet will prescribe antihistamines or corticosteroids to block the reaction and give immediate relief.  Antibiotics will be prescribed for secondary infections. 

Inhalant allergy
Some of these allergies are seasonal (grass and tree pollens) others occur all year round (mould, dust mites).  Conversely, to humans where this type of allergic reaction manifests itself in respiratory problems, in dogs the symptoms can include allergic rhinitis but mostly result in itchy skin (pruritis).  Protection from these allergens is often impossible as they are generally environmental, so management of the symptoms is the key to success.  Treatments include:

• Anti-inflammatories
• Fatty acid supplementation in the diet
• Newer drugs exist to block the chemical signals associated with the itch – your vet can advise
• Shampoo therapy
• Desensitisation therapy: the allergens need to be identified by allergy testing

Food allergy

These allergies don’t respond well to medical treatments, so success lies in identifying the offending component(s) in the diet through an elimination trial using a hypoallergenic diet.  It’s important that the recommended diet is fed exclusively for at least 8 weeks otherwise it’s not a valid test, so all extras, treats and flavoured vitamins must be discontinued.  You need to consult with your vet if your dog is on medication for a non-associated condition.

Contact allergy
This is the least common type of allergy in dogs and results from direct contact with the allergen(s), such as pesticides, grasses, or materials used in carpets and bedding. Symptoms are skin irritation at the points of contact – usually the feet and tummy.  Removal of the allergen – if it can be identified – usually resolves the problem.

Dealing with allergies can be time-consuming and identifying the allergen(s) can be lengthy and frustrating.  Remember that repeated treatment with anti-inflammatories, particularly corticosteroids, can exacerbate the problem by depressing the immune system.  Successful treatment of allergies often involves not only veterinary medication but complementary therapies, diet change and environmental change.

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About Heather Giles

Heather Giles is PR & Marketing Manager for Hilton Herbs.  Heather has worked for the company for over 20 years and her job includes trade shows, working on the website, organising product photography and being responsible for advertising in the UK.