Pete the Vet: How to get rid of your dog's irritating itch

A change in diet can help but it's not the only answer

Diet can be a factor in 20% of itchy dogs

Itchy skin in dogs is common, and it isn’t always solved easily. It’s no surprise that there are internet-driven “quick fixes”: people want to help their pets as rapidly and easily as possible. It can be tempting to fall for any idea that sounds plausible.

The “raw diet” phenomenon is a good example of this. There are anecdotes of itchy dogs changing from a standard commercial diet to a raw meat diet, resulting in an instant resolution of the itchiness. As a vet, and as a scientist, I am interested to hear stories of cases like this, but I also want to explain the science behind them.

Itchy skin does not happen spontaneously: there is always an underlying reason for the itch, and this is known as the “primary cause”. The aim of a vet is to identify this cause, and then to remove it from the dog’s life or to use medication to minimise the itch.

Food allergy is the reason why around 20% of itchy dogs develop skin disease. So in one-in-five itchy dogs, if you change the diet, there’s a good chance that the itch may be cured. This is the reason for those anecdotal cases of raw diet solving itchy skin. The other side of this data is equally important to remember: in 80% of itchy dogs, changing the diet will not help.

It’s also important to remember that a raw diet is not the only possible answer in such cases. In food-allergic dogs, the itchy skin occurs as a result of an allergic reaction to a specific ingredient in the diet, most commonly to a protein. Studies show that the most common dietary ingredients to cause allergic reactions are: beef (34%), chicken (17%), lamb (15%), and wheat (14%). So by just removing these four ingredients from your allergic pet’s diet, you have an 80% chance of stopping the problem. On the occasions when a raw diet helps, it’s because a specific protein is used (e.g. turkey) and your dog is not allergic to that protein.

When vets are investigating food allergy as a possible cause of itchiness, they tend to take a different approach: instead of suggesting a raw diet, they usually recommend a so-called “hydrolysed” diet. This is a commercial diet that has been pre-digested, so that it no longer contains protein chains long enough to prompt an allergic reaction. This is more likely to be successful than a raw diet, because it’s almost guaranteed to stop all food allergic dogs from itching, as it does not contain any allergens. A trial of 6 – 8 weeks is usually enough: if your dog stops itching in this time, it’s likely that the cause was, indeed, food allergy. If they continue to feel itchy despite eating nothing but the special diet, it’s highly unlikely that food allergy is the cause.

As well as the fact that hydrolysed diets are the gold standard when diagnosing food allergy, vets also have reservations about raw diets generally: raw meat often contains bacteria that can be dangerous to humans, and these bacteria can become widely disseminated around the home, on dogs’ muzzles, coats and in their bowls. If any humans in the household are vulnerable (e.g. young children, elderly people or those on chemotherapy), there is a significant risk of human health issues linked to the bacteria from raw meat. This may be a risk that can be successfully managed, but it’s important to be aware of it.

It’s also important to remember that 80% of itchy dogs do not suffer from food allergy: changing the diet will not help these animals. Other common causes of itchy skin include external parasites (such as fleas and mange), allergies to dusts and pollens (so-called “atopic dermatitis”), and direct contact irritation and allergies (e.g. dogs with itchy feet and a rash on their underside, caused by sensitivity to grass or vegetation). Often, the initial primary cause of itchiness is complicated by subsequent secondary infection of the damaged skin with yeasts and bacteria. Even if the original cause is removed, a dog may continue to itch because of these infections if they are not properly treated. This is why visiting your vet is likely to provide the quickest fix for your pet.

Apart from food allergies, nutrition does have an ongoing general role in skin disease in dogs: a daily supplement with omega-3 fatty acids (such as Mackerel Oil) can help the barrier function of the skin, reducing the impact of allergies and lowering the risk of secondary complications like those bacteria and yeast infections. Regular shampooing can also help itchy dogs in a general way, using a product designed for use in dogs (human skin and hair has a different pH to the canine equivalent).

The good news is that most itchy dogs get better within three visits to the vet, although lifelong ongoing anti-inflammatory medication is needed in some cases. Rarely, some obscure cases may need to be referred to veterinary skin specialists (such as Cork-based Skinvet Ireland – www.skinvet.ie).

Last week I mentioned new forms of treatment for arthritis in pets: there have been similar advances in the way that allergic skin disease is now treated. Traditional anti-inflammatory medication such as prednisolone tablets can cause significant side effects with long term use, and a more recent addition to the vet’s pharmacy, cyclosporine, can be more effective. Even more recently, drugs that inhibit specific inflammatory biochemicals have been introduced: the most recent is a once monthly monoclonal antibody injection that targets these “itch-inducing” molecules in your dog’s body, helping allergic skin disease with minimal side effects.

Raw meat diets do have a place, but they are not a cure-all for dogs with itchy skin.