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Canine Skin Allergies

Canine pruritus is a very fancy way the Veterinary world terms itchy dogs and it is one of the main reasons owners take their canine companions to the Vet. What is it exactly that causes this itching? Why is it sometimes so seasonal? The fact is that dogs, like humans, are very susceptible to skin allergies and it is important for owners to realize that this is the case, and that in most of these instances a skin allergy is managed, not cured.

First and foremost, it is very important to realize that there are FOUR main causes of canine skin allergies and these allergies are often behind any hot spots or rashes that form on dogs. Each one of these allergies requires different ongoing management, and in many cases a dog will have more than one allergy at a time, which can complicate things, particularly for the Vet when we come to try and diagnose the exact cause of a dog's itch or skin problem.

These allergies are:

  • Flea allergies
  • Contact allergies
  • Food allergies
  • Atopy (the canine version of eczema) Flea

Allergy Dermatitis

Flea allergy dermatitis is by far and away the most common canine skin allergy. While many dogs can handle the odd flea on them, dogs with a fleaskin alergies allergy dermatitis very quickly become very itchy! Typically these dogs are primarily itchy over their necks, back and at the tail base – as this is where the majority of fleas live and feed! This allergy is caused by the dog's immune reaction to the injection of the flea's saliva into the skin whenever it bites the dog. This is why it may only take one or two flea bites to set the immune system into overdrive causing a body-wide skin reaction. As fleas tend to be more active in summer and early autumn, this tends to be more of a seasonal problem, which can also aid a diagnosis. The key to ruling this problem out and keeping on top of it, is strict and regular flea control – preferably with a topical product like Advantage or Frontline that kill's flea larvae and eggs as well as the adult fleas. On top of this, flea bombing the house and washing your dog's bedding is also very helpful.

Contact Allergy Dermatitis

A contact allergy is caused by a dog's skin coming into contact with foreign objects that again the immune system reacts to in an excessive manner! The main causes of a contact allergy are in fact plants and long grasses. Wandering dew is by far and away one of the main culprits here. Because of the fact plants and pollens are often to blame, owners often find that this itching is seasonal, as it is with a flea allergy dermatitis. There are many other chemicals that can also cause a contact allergy including flea collars, bleaches, carpet cleaners and fertilisers. Typically a dog with a contact allergy will be very itchy underneath the belly, in the armpits and groin, as well as between the toes and sometimes on the muzzle. If your dog has been walking in long grasses or bouncing through plants and shrubs and has developed a rash, this is the most likely cause!

It can often be quite difficult to pinpoint the exact cause of the contact allergy and oftentimes there is more than one culprit. Thankfully there is a new technology available where your dog can be desensitized to certain pollens, chemicals and plants via a 'vaccination' made against the cause or causes of the problem. This is carried out by a Veterinary dermatologist and usually requires a skin test first where many different known allergens are injected under the dog's skin to assess the bodies reaction to each one. The best treatment of course is avoidance – however this can often become impossible if the cause is a plant your have an abundance of out in the back yard!

Food Allergies

The canine food allergy is often a difficult problem to diagnose, however once diagnosed and a change in food started, the results are usually fantastic. Just like the above allergies, a food allergy is caused because the dog's immune system over-reacts to certain proteins in the dog's diet. Most of the time these are proteins found in beef or lamb products, however dogs can have food allergies to all sorts of foods including chicken and even wheat! A food allergy usually causes body wide itching in no specific area.

As these allergies are a lot harder to pinpoint and diagnose directly, most Veterinarians decide to carry out a 'food trial' with these dogs.  Thankfully there are several very good diets available for dogs with this problem. They all basically work on the same principle. Because the immune system recognizes the proteins in the food as foreign – the food companies have found that by hydrolyzing (or making these proteins very small), the immune system can no longer recognize them. These new, small and indictable proteins do not cause any reaction from the immune system and hence dog's with food allergies respond well and quickly to these products. A food trial is undertaken with this food ONLY for three weeks and after this time other foods may be added in one by one, week by week, by your Vet in order to try and pinpoint the food or foods to blame.


Atopy is basically the canine version of eczema. Again this is a problem where the dog's immune system over-reacts, however in this case a different form of reaction takes place which causes the dog to have an ongoing desire to itch and lick him or herself making the dog very uncomfortable. Just like a food allergy – dogs with atopy are generally itchy everywhere. This syndrome is often difficult to diagnose directly and is often diagnosed by excluding the other allergies mentioned.

Treatment is either ongoing low dose steroids to help stop this excessive immune response, or another new drug recently available within the last 2 – 3 years called "Atopica". This is a drug called cyclosporine which acts much like steroids do, but without the side effects we commonly see with excessive use of them. Although this treatment is a little more expensive, it is by far and away the best current treatment available for this problem.


As stated above, most of these problems are managed, NOT cured (at this stage of Veterinary medicine anyway). In all of these cases a topical antibacterial, anti-inflammatory cream is always helpful for reddened and broken areas of skin and your Vet can prescribe some of this cream for your dog in these instances. He or she may also want to give your dog a short course of steroids or a steroid injection to help take the inflammation out of the skin and make your dog more comfortable at home, as well as prescribe a course of antibiotics ideal for skin infections. There are also several very good medicated shampoos currently on the market which are also ideal for this. Also don't forget that a dog can have one or all of the above allergies, and it is important your Veterinarian helps to work through this with you.

Other Causes of Canine Pruritis

Of course it is important to remember that although these allergies are common, they are not ALWAYS the cause of itching in dogs. Skin mites and other parasites as well as many other causes of bacterial or fungal infections can also cause intense itching without an allergic basis, and this is where Veterinary medicine steps in to attempt to diagnose the exact cause of the problem. As above, this can include anything from skin biopsies, to food trials, to skin scrapings or even just treatment trials with steroids. Ultimately your Vet has your dog's best interests in mind and will consider all the possible causes for itching before coming up with a diagnostic plan in order to get the best treatment for your boy or girl!

When your dog does actually need a veterinary visit, it is important not to book in too many routine things in one go! If a dog is having multiple vaccines, split these up so they don't all have to be given on one day. Likewise, it wouldn't be the best idea to book your boy or girl in for a nail clip, vaccinations, ear cleaning and a grooming! Keep the routine procedures light for a while. Likewise if you have a very anxious of fearful dog, if you can put off these routine procedures, do!

Finally I always encourage my clients to handle their dogs at home and carry out "fake exams". This means flipping the lip and having a look at his or her teeth, checking in the ears, feeling the legs and between the toes on each paw, feeling the abdomen and picking your dog up and put him or her on a table!! If you can do this several times a week with rewards for good behaviour then this will definitely put you in good stead for the actual physical exams your Vet carries out.


Remember to keep these main four canine allergies in the back of your mind when you next see your dog scratching, and if you suspect one of these in your boy or girl, be sure to consult with your local Veterinarian about further workup to confirm or deny your suspicions!

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Thursday, 29 February 2024

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