Toxic Foods

November 6th, 2008

Chicken, fish and wheat can be toxic to canines. Nadia Crighton takes a look at foods that cause negative reactions and poisoning in our dogs.


We all love to treat our dogs, and who isnt guilty of sharing a tasty morsel or two from the living room couch while watching our favourite flick with our beloved dog? The problem is, some treats particularly human ones can be very bad for our dogs and in some cases, even fatal.


With so much information out there on whats good and bad for our dogs health, it is easy to get confused. Dogs Life catches up with specialist veterinary dermatologist Linda Vogelnest from the University of Sydney to find out the causes of negative food reactions and what the main culprits are.

Proteins are the usual problem, with beef the most common, Vogelnest says. But chicken, lamb, fish, dairy, wheat and soy allergies have all occurred. Most dogs are only allergic to one particular protein and rarely multiple.

Testing for allergies

Wouldnt it be great if Rover could let us know what foods were bothering him? But because our canine companions can’t relay to us what foods make them feel a little off, it is not until they are experiencing consistent symptoms after ingesting the foods several times that we realise there is a problem. Testing is also not an easy feat.


Unfortunately, there are no current tests that clearly identify food or airborne (pollen/dust mite) allergies in dogs, Vogelnest tells Dogs Life. We make the diagnosis of food allergy by seeing clear improvement on strict elimination diets consisting of a new protein, not previously fed (eg, kangaroo), then a clear relapse of signs again on reintroducing the old diet. Vogelnest recommends sequentially introducing individual foods one week at a time to find the offenders.

For airborne allergies, it is a little more complex, and we need to have consistent signs from the history of changes in that pet, together with itch or lesions in the typical areas. We must rule out other possible diseases that can look like this allergy before being certain of the diagnosis, Vogelnest says.

When allergies are affecting the skin, the investigation to find the cause is ideally done through a veterinary dermatologist. Skin allergies are fairly complex, and clearly determining a diagnosis is the most important step to guide what treatments are most likely to be effective, Vogelnest suggests.

Once the offending food has been found, it is easily treated. Treatment is very easy with food allergy, as avoiding the problem food(s) will result in total cure of the problem, Vogelnest says. This obviously requires accurately identifying the problem foods, so the hardest part is stepping through the sequential food re-challenge, where we test one food at a time each week and then the final treatment is very easy.

Comfort foods

It is widely known to many that chocolate, particularly cooking chocolate, is a big no-no for dogs and cats. It can have terrible repercussions and can even cause death in large amounts. But to the average dog owner and dog, this can be very confusing, particularly considering you can purchase doggy chocolate, which is not ideal, but safe for dogs!


However, other human foods can also cause problems for dogs. Many of our human comfort foods are certainly not ideal for our dogs, as they are not part of a balanced diet, Vogelnest says. In addition, some foods are actually dangerous: chocolate (in particular cooking chocolate) can be fatal for dogs and cats (although they do need to eat a reasonable amount to be a serious risk) and should never be fed. Grapes can cause severe kidney damage, and onions or garlic in large amounts can cause blood cell damage.

However, this is not to say that foods, such as ice-cream, lollies etc, don’t also have their side effects it might just take a little longer to show. Obesity is a huge problem amongst our doggy population, and feeding our pets treats the human or canine kind can also have huge implications on our pets health.

There is a large range of doggy treats more suited to our pets now available for sale, however, many of them contain high amounts of fat and can cause havoc with maintaining a good body weight, Vogelnest warns.

As with owners, diet is particularly important in maintaining good health in our dogs. A good and consistent diet is also an excellent way to keep tabs on negative food reactions, as it is much easier to tag what foods are causing what reactions when you know whats in the diet. Changing your dogs diet frequently can cause tummy upsets and make identifying a problem difficult.

As for people, a balanced diet contains all the essential nutrients, vitamins and minerals to maintain healthy bodies, so its just as important for our dogs as ourselves, Vogelnest advises. Diet plays a vital part in our ability to maintain good health, help avoid diseases and illnesses, and keep us bright and alert. Poorly balanced diets often have influence gradually over time, rather than acutely.

Allergy research

So why do dogs suffer from food reactions? And are the people in the know seeing more of this problem on a regular basis? The good news is that Vogelnest hasnt noticed an increase, particularly in food allergies.


I do not think I am seeing an increase in food allergies. Overall, they remain much rarer in dogs than airborne allergies (pollen/dust mite allergies), she says. I probably see one dog with food allergy to every 40 to 50 with airborne allergies in my dermatology practice.

Perhaps it seems more dogs are suffering from allergies as its much more widely discussed today than 10 years ago. As our pets become more integral members of society, the scratching family dog is much more likely to have specialised care to prevent the problem than ever before. Because of this, animal researchers are working hard to find out why food allergies occur in the first place.

There are ongoing studies into food allergy in dogs, and as yet, the exact change in the immune system that occurs with food allergy is not clear in dogs, although it has been clearly determined in people and in cats with food allergies, Vogelnest says. For this reason, we sometimes refer to recognised changes to diet as food reactions rather than allergies, as an allergy implies the immune system is at fault, and as yet we haven’t clearly determined this in dogs. Work in this area is definitely continuing.


Many people have read misinformation about food reactions in pets. Some believe dogs can’t be allergic to chicken, while others are certain that a small morsel of garlic, which is great for fighting off fleas, can be fatal to a dog. So what are the facts?


The fact is, dogs can be allergic to chicken and I recognise this fairly regularly, Vogelnest says.

She is also quick to remind Dogs Life readers that food reactions tend to be caused from the foods that we feed commonly to our dogs. This makes sense when you think that it takes exposure of an individual food over some time for an allergy to develop, Vogelnest says. People often think it could be some new ingredient or food fed recently (eg, a new brand of dog food) but this is in fact the least likely cause.

Vogelnest also points out that commercial foods, in most cases, contain a mixture of proteins, so even chicken and rice flavoured dry food will often contain beef in some form. Meat by-products can be whichever meat was available and economical at the time to buy, she says.

Always check carefully on the label to see what you are really purchasing. But what about garlic?

Garlic in small amounts is fine, but large amounts can cause problems. A whole garlic bunch for little Chihuahua would be dangerous, she says.

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