Allergic Disease in Dogs

By Dr. AJ Warren

What is an allergy?

An allergy is an abnormal over-reaction of the immune system to a normally benign substance. The body has to be exposed to a substance at least once to form an allergy to it, which is why sometimes an animal may present with an allergic reaction to a substance, even if they’ve had no prior reaction.

Some breeds are more pre-disposed than others, and different animals will respond differently to different treatments.

What does it look like?

Allergy can present itself in many different ways;

• Itchy / scabby skin
• Excessive licking or gnawing paws ( or red/pink fur around paws )
• Excessive licking or gnawing underarms or groin ( or red/pink fur around these areas )
• ‘Sweaty’ or yeasty smell
• Recurrent ear infections
  • During allergic flare-ups the skin inside the ear becomes moist and inflamed which is a perfect breeding ground of bacteria.
• Hair-loss due to constant scratching
• Vomiting & Diarrhoea without other explanation (e.g. scavenging)

What can my dog be allergic to?

There are two  main kinds of allergic disease;

1. Environmental allergies (e.g. dust mites ) which will often present as a skin disease
2. Dietary allergies (e.g. to chicken) which may present as skin disease or gastro-intestinal disease, or both.

Many dogs will have a mix of both environmental and dietary allergies, and it is important to remember that if this is the case, they may only respond partially to specific allergy-targeted therapy.

Environmental Allergies

Environmental allergies may be seasonal or year-round. Common allergies include dust, dust mites, pollens, grasses, weeds and molds. A blood test done by your vet can help to determine what specific environmental allergens your individual dog is allergic to.

An injection called Artruvetrin can be tailor-made to your individual pet’s allergies and can help build up immune-tolerance to their specific allergies, so they do not react as strongly (or at all!)

Dietary Allergies

Dietary allergies are often seen year-round, although they may wax and wane if you swap and change foods. This may be due to different types or concentrations of proteins (e.g. chicken vs salmon) or how broken down the proteins are (cooking protein molecules alters the shape). They can only be properly diagnosed with a specific dietary trial.

A dietary trial consists of exclusively feeding an anallergenic food containing hydrolysed (broken down) proteins. This gives the body all the molecules it needs without ‘activating’ the immune system (it does not recognise the protein strand). We feed this for 8-12 weeks and observe for response. If there is no improvement then the diet is likely not the cause of the allergy. If the animal improves, we know that at least some of the allergic reaction is due to the diet. From this point we can slowly introduce different ingredients and observe for reaction until we have a list of food’s they cannot eat.

There are many common misconceptions about dietary allergies in dogs, some of which are addressed below; as always it is best to consult your veterinarian before altering your pet’s diet, especially if a diet trial has not been performed.

• Myth : Grain free diets are good for dogs with allergies.
• Fact : Most dogs are allergic to the meat protein (chicken, turkey, lamb etc) and not the grain. Long term use of grain free diets have been associated with increased risk of heart disease (Dilated Cardiomyopathy).

• Myth : RAW diets are better than kibble.
• Fact : RAW diets are often nutritionally unbalanced and should only be fed if working alongside a board certified, veterinary nutritionist*. They can pose health risks to your pet due to the high level of bone meal (impaction risk) and potential parasite eggs. They are also associated with human health risks due to due to their high levels of salmonella and campylobacter. Some dogs may respond to a RAW diet because the proteins have not already been broken down by the cooking process so the body may not react as strongly, but you may find a similar or better result using a novel protein (e.g. ostrich) or an appropriately hydrolysed kibble without all the risks and side effects!
  • * Dr Marge Chandler DVM MS MACVSc DipACVN DipACVIM DipECVIM-CA MRCVS Moorview Referrals is one of the best known nutritionists in the UK and offers a service to help with your pets nutritional needs.

• Myth : Boutique / novel diets are better for dogs
• Fact : Large, reputable companies invest a lot of time and money into ensuring their product is a complete diet whereas there is often less research done for the smaller/boutique brands. If in doubt always go for a well known, reputable company and if you have any questions always contact the Pet Food Manufacturers Association (PFMA) and ask if your chosen diet meets the basic nutrition requirements.

Alternative Treatments

Understandably, full diagnostics are not for everyone. They can be cost-prohibitive, time-consuming and results are not guaranteed. Some owners prefer to simply treat the symptoms, regardless of the root cause. There are three main treatments available.

Steroids ( Prednisone, Medrone-V etc )

Work when given at anti-inflammatory doses to reduce itching and help break the itch-scratch cycle.

Apoquel (Oclacitinib)

Targets specific cytokines (signalling molecules) that cause itch and inflammation,

Cytopoint  (Monoclonal Antibody)

Breaks the itch-scratch cycle by neutralising histamine molecules before they can cause allergic itching.

Additional Measures

Even if your pet does not have an active allergy to flea saliva it is important to keep on top of parasite prevention. A single flea bite will still release ‘itch’ molecules (histamine), so inadequate parasite prevention can make it harder, or more expensive, to control allergies. 95% of fleas do not live on the animal but instead will live in the environment; only jumping on the animal to feed. So even if you don’t find live fleas on a pet it is worth considering using a good preventative treatment plan.

For best results use a POM-V (veterinary strength) flea preventative such as Bravecto (every 12 weeks), Advocate (every 4 weeks) or Nexguard (every 4 weeks). Some dogs with exceptionally sensitive skin may prefer a tablet over a spot-on treatment. Some dogs may benefit from a Seresto collar; this is the only POM-V collar that actually repels fleas and ticks and can last 7 – 8 months.

Remember! Fleas do not die out in winter – especially in houses with central heating and good insulation. It is important to appropriately dose your pet year round. It is often worthwhile to use an insecticidal spray ( E.g. Indorexx, R.I.P spray ) every 6 – 12 months to help kill those in the environment to stop them biting your pet.

It is important to ensure the environment is also adequately treated. Hot-wash dog bedding regularly (minimum 60*c) and ensure you rinse bedding very thoroughly. Ensure regular hoovering to remove microscopic parasite eggs, dust mites and other allergens from carpets / sideboards etc. Avoid strong cleaners, aerosols and other potential irritants that may cause a contact allergy.

Bathing your dog in a soothing dog-specific shampoo may sometimes be of benefit. It is important to always use a shampoo designed for dogs as their skin pH is different to ours. Avoid bathing your dog more than once a month as this can disrupt the normal, healthy skin flora. Coatex Aloe Vera is particularly good but you may find other brands work as well. Talk to your veterinary surgeon about recommended brands.

Avoid using Tea-tree oils or shampoos, Dettol, harsh antiseptics or other anti-bacterial products designed for humans or home use; this is very harsh to dog’s skin and can be irritating to any dog’s skin. Hibi-scrub and malaseb should be used sparingly and only under direction from your vet if your dog has a skin infection; they are both excellent antibacterials but they will dry out the skin and destroy the good skin bacteria as well – both of which cause itching!

Similarly, avoid using at-home topical treatments such as coconut oil; these may coat the hair protein and make it seem shiny and healthy, but it doesn’t have much more than a cosmetic effect. Similarly, coconut oil (and fish oil, olive oil etc) is very fatty – if ingested there is a risk of causing pancreatitis.

Omega 3’s and 6’s can be very beneficial for skin health but these are best given orally with a skin supplement specially designed for dogs. Lintbells and Nutraquinn are good brands, although the PSDA also has a reasonably good own-brand supplement.

Anti-histamines (e.g. Piriton) have limited efficacy in dogs; they may do a small amount, but it’s believed that as they are formulated to work against the human histamine molecule, they don’t quite ‘fit’ the canine histamine molecule and therefore may not work.

If you have any questions or concerns regarding your pets allergies or treatments, do not hesitate to contact your veterinary surgeon.