Skin allergies (atopic dermatitis) are common in dogs and cause them to feel itchy. This itchiness makes them chew, lick and scratch at themselves causing significant self-trauma. The allergy is normally triggered by something in the environment, such as food, fleas, pollens and dust mites. Sometimes it is possible to identify and stop the dog having contact with this allergen (e.g. changing to a special diet), but on many occasions this is not possible, for example with allergies to pollens and dust mites. In these cases, medication is usually needed to help control the itchiness and reduce the frequency and severity of flare-ups.
What causes allergic skin disease?
In dogs with skin allergies, their immune system is having an over-the-top reaction to a harmless foreign substance that the dog encounters within in its environment. The three typical causes of skin allergies are:
- Flea allergic dermatitis (FAD): in this condition the dog is allergic to flea saliva. Therefore, when they are bitten by a flea they are extremely itchy, causing them to scratch and chew at themselves. The condition results in skin that is red, inflamed and scabby, as well as thinning of the coat and bald patches. The area of the body normally most affected in FAD is around the back end of the dog (the area that would be covered by trousers, if they were wearing them!). This is because this is the area where the fleas tend to mainly hang out.
- Food allergens: dogs can be allergic to certain ingredients in their diet, which can cause itchy skin and also gastrointestinal signs. Dogs with food allergies tend to me most itchy around their head, ears and paws.
- Environmental allergens: dogs can be allergic to things within the environment such as certain pollens, dust mites and mould. These allergies are often seasonal, and dogs are normally most itchy around their ears and paws (as with food allergies), but other areas can also be affected.
It is thought that dogs with skin allergies may have a poorer skin barrier function, which is further impaired by them licking, chewing and scratching at themselves. This self-trauma often results in skin infections, which are itchy in themselves and can lead to further self-trauma; hence skin allergies are often a viscous cycle and can be challenging to break.
While skin allergies can affect any breed, West Highland White Terriers, Bichon Frises and Shar Peis are particularly prone. Skin allergies normally develop between 3 months and 6 years of age.
What are the symptoms of skin allergies?
The symptoms of skin allergies generally include:
- Red, inflamed or scabby skin
- Skin rash (often seen on the tummy)
- Flaky or scaly patches
- Thinning or loss of hair (normally due to self-trauma)
- Recurrent ear infections
- Pink saliva staining to the fur where the dog is persistently licking e.g. feet
- Thickened skin
- Pigmented skin
- Bad skin odour
- Vomiting and diarrhoea can be seen with food allergies
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How are they diagnosed?
The vet may be suspicious of a skin allergy based on the clinical history and physical examination. Recurrent ear infections and a dog that persistently licks at their paws are common clues. Determining the cause of the allergy can be much trickier. The vet will want to rule out an allergy to fleas first and this can be easier to deal with than food or environmental allergies. They will check for fleas and flea dirts, and will ask whether they are up to date with flea treatment.
Food allergies are normally investigated by doing a strict food trial, whereby the dog is either fed:
- A completely novel diet containing proteins that the immune system would not have encountered before e.g. Hills d/d, which contains venison and potato OR
- A hypoallergenic diet where the protein has been broken down into tiny pieces so that it is no longer recognised by your dog’s immune system. The term ‘hypoallergenic’ is used very frequency, so you need to be careful that you are buying the right type of food for your dog’s food trial. A good example is Hill’s z/d or Royal Canin Anallergenic – these are available to buy from our Shop.
If your dog’s symptoms resolve during the food trial, then you are technically supposed to challenge them with their old diet to see if their symptoms return, thereby confirming a food allergy.
Investigation of an environmental allergy (e.g. pollens and mould) is carried out using a skin prick test (intradermal skin testing) – this is normally carried out by a specialist dermatologist.
Treatment for skin allergies
The treatment will depend on the cause of the skin allergy:
- Flea allergic dermatitis: rigorous flea control is needed, along with treatment of the environment and all other animals in the household (please see our FAD info sheet).
- Food allergies: these are treated by switching the dog to a novel protein or hypoallergenic diet for the long-term. They may still have flare ups if they eat something that they shouldn’t.
- Environmental allergy: these tend to be the most difficult to treat, as the allergen cannot usually be avoided. The results from intradermal skin testing can be used to make a special vaccination for your dog. These injections can be used to desensitise them to whatever allergens they are allergic to. This can work well for some dogs, but does not work for others. Injections must be continued monthly.
Various medications are available for dogs with allergic skin disease, to reduce the itchiness. Traditionally vets have used steroids, but these have lots of side effects so are best not used for long-term use, if possible. Newer medications are now available (in both tablet and injectable forms) that have a much more targeted effect on the itch receptors, making the dog more comfortable without having the side effects of steroids. Please talk to your vet about the treatment options available for your dog.
Environmental skin allergies can be seasonal (depending on what the dog is allergic to) so it may be possible to just use mediation when the dog has a flare up, rather than needing to use it all year around.
Sometimes antibiotics will need to be prescribed if there is a skin infection is present (usually as a result of self-trauma to the skin). Omega-fatty acid supplements can also be beneficial in helping to control skin allergies, by improving the skin barrier function. Again, these are available to purchase in our shop.