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For Your Pet: Is That A Treat Or A Poison?


By Nurse Mark

We often are asked questions about pet health, and even though we are not trained in the veterinary arts we will usually do our best to provide a well-researched answer. Sometimes conventional veterinary medicine, like conventional human medicine, runs out of answers and drugs to throw at a problem and pet owners turn to alternative medicine for solutions.

We have some friends locally who recently and tragically lost a beloved dog. They are now understandably concerned for the well-being of their other animals, and asked Dr. Myatt what she would do for what appeared to be an allergic reaction in another of their dogs. Dr. Myatt suggested Grape Seed Extract which she has used successfully in our own animals. Our Border Collie used to suffer from occasional asthma attacks, and Dr. Myatt would give the dog a Grape Seed Extract capsule in a ground meat treat for very prompt relief of this. Our across-the-road neighbor has a cat who was put on steroids for allergies and was still miserable. We suggested Grape Seed Extract and Fish Oil sprinkled over the cat's food. Sure enough, this provided what our neighbor friend described as "miraculous" relief returning the cat from misery to it's former happy affectionate self.  We told our friends of this, and sent them home with a few capsules to try.

Being conscientious folk, they thought about what they were going to give their dog and remembered something troubling: There have been reports of dogs becoming ill and even dying after eating grapes, raisins, and sultanas. They emailed us, quite worried, to ask about this - and rightly so.

Dr. Myatt explained that she was not aware of anything in grapes that should be toxic to dogs - in fact we have fed our own 3 dogs occasional grape treats without any ill effects.

Grape Seed Extract should be quite non-toxic as the active ingredient is proanthocyanidin or pycnogenol. In fact, Grape Seed Extract has more of the active ingredient proanthocyanidins ("OPC's," also called pycnogenols) than pine bark extract which also has a long history of safety and successful use in humans.

Still, I wanted to be sure that we were not recommending something that could harm our friends or anyone's pet, so I did a little research. Again, I must say that we are not trained in the veterinary arts, and so this must not be taken as veterinary advice. What follows is what I have discovered as I searched to find whether there was any fact to the Dog Poisonings By Grapes:

Interestingly, this appears to be a relatively recent problem. The first cases of grape poisonings in dogs were reported in 1998, and it wasn't until 2001 that the American Society for the Prevention of Cruelty to Animals Animal Poison Control Center (APCC) in Urbana, Illinois had enough solid reports to issue a warning about this. Further, a thorough review of available literature, reports, internet bulletin boards and chat forums and other sources indicates that not all dogs seem to be affected, or perhaps that not all grapes cause the problem, or that perhaps it is dose-related in some way. There are any number of theories being postulated, from pesticides to GMO's to bacteria and more.

One theory that did seem to make sense is that some grapes and raisins may become infected with Ochratoxin A, a nephrotoxic compound produced by the black aspergillus species of mold. It is certainly quite toxic for people. People would not likely eat moldy grapes, but dogs might devour them, especially if they are "chow-hounds" like ours. The biggest risk for people is related to grape juice consumption. Small children bear the highest risk consuming occasionally comparatively large quantities of juice and raisins. The toxin is found preferentially in grape products from more southern locations. The mold that produces this toxin might not even be noticeable on a grape or raisin, and it may be that dogs are even more sensitive and susceptible to illness from this toxin than people. It might also be well to remember that even though mold can be washed off a food, the toxins produced by that mold usually cannot - a moldy item should be discarded.

Our Grape Seed Extracts are pharmaceutical grade preparations, and would certainly not contain Ochratoxin or any other contaminant!

Along with all this research into grapes I came across a number of other things that we humans can eat but that are toxic to dogs, cats, and other pets.

Some of these things include:

Xylitol - a common and healthy sweetener for humans is very toxic to dogs and other animals.

Chocolate which contains theobromine, a compound that is a cardiac stimulant and a diuretic. (May also be sweetened with xylitol!)

When affected by an overdose of chocolate, a dog can become excited and hyperactive. Due to the diuretic effect, it may pass large volumes of urine and it will be unusually thirsty. Vomiting and diarrhea are also common. The effect of theobromine on the heart is the most dangerous effect. Theobromine will either increase the dogís heart rate or may cause the heart to beat irregularly. Death is quite possible, especially with exercise.

After their pet has eaten a large quantity of chocolate, many pet owners assume their pet is unaffected. However, the signs of sickness may not be seen for several hours, with death following within twenty-four hours.

Cocoa powder and cooking chocolate are the most toxic forms. A 22 lb dog can be seriously affected if it eats a quarter of a 8 oz package of cocoa powder or a 4 oz block of cooking chocolate. These forms of chocolate contain ten times more theobromine than milk chocolate. Thus, a chocolate cake could be a real health risk for a small dog. Even licking a substantial part of the chocolate icing from a cake can make a dog unwell.

Semi-sweet chocolate and dark chocolate are the next most dangerous forms, with milk chocolate being the least dangerous. A dog needs to eat more than a 8 oz block of milk chocolate to be affected. Obviously, the smaller the dog, the less it needs to eat.

Onions and garlic are other dangerous food ingredients that cause sickness in dogs, cats and also livestock. Onions and garlic contain the toxic ingredient thiosulphate. Onions are more of a danger.

Pets affected by onion toxicity will develop hemolytic anemia, where the petís red blood cells become damaged.

At first, pets affected by onion poisoning show gastroenteritis with vomiting and diarrhea. They will show no interest in food and will be dull and weak. The red pigment from the damaged blood cells appears in an affected animalís urine and it becomes breathless. The breathlessness occurs because the red blood cells that carry oxygen through the body are reduced in number.

The poisoning occurs a few days after the pet has eaten the onion. All forms of onion can be a problem including dehydrated onions, raw onions, cooked onions and table scraps containing cooked onions and/or garlic. Left over pizza, Chinese dishes and commercial baby food containing onion, sometimes fed as a supplement to young pets, can cause illness.

Onion poisoning can occur with a single ingestion of large quantities or with repeated meals containing small amounts of onion. A single ingestion of 1 to 1 1/2 lbs of raw onion can be dangerous and a 22 pound dog, fed 6 ounces of onion for several days, is also likely to develop anemia. The condition improves once the dog is prevented from eating any further onion

While garlic also contains the toxic ingredient thiosulphate, it seems that garlic is less toxic and large amounts would need to be eaten to cause illness.

(As a side note, Dr. Myatt has successfully used garlic cloves in treating a large breed dog that was suffering from "Valley Fever" (Coccidioidomycosis - a respiratory disease common in Arizona) and was unresponsive to conventional antibiotics. Garlic has long been recognized as a potent natural antibiotic, and cleared this dog's problems up very quickly.)

Macadamia nuts are another concern. A recent paper written by Dr. Ross McKenzie, a Veterinary Pathologist, points to the danger of raw and roasted macadamia nuts for pets.

The toxic compound is unknown but the affect of macadamia nuts is to cause locomotor difficulties. Dogs develop tremors of the skeletal muscles, and weakness or paralysis of the hindquarters. Affected dogs are often unable to stand and are distressed, usually panting. Some affected dogs have swollen limbs and show pain when the limbs are manipulated.

Dogs have been affected by eating as few as six macadamia nuts, while others had eaten approximately forty nuts. Some dogs had also been given macadamia butter.

Luckily, the muscle weakness, while painful, seems to be of short duration and all dogs recovered from the toxicity. All dogs were taken to their veterinarian.

Other potential dangers include:

The kernels (pits) of plums, peaches and apricots, and apple seeds (these contain cyanogenic glycosides which can resulting in cyanide poisoning)
Potato peelings and green looking potatoes
Rhubarb leaves
Moldy/spoiled foods
Yeast dough
Coffee grounds, beans & tea (caffeine)
Hops (used in home brewing)
Tomato leaves & stems (green parts)
Broccoli (in large amounts)
Cigarettes, tobacco, cigars

Avocados and dried beans are dangerous to pet birds. The skin and pit of avocados had been known to cause cardiac distress and eventual heart failure in pet bird species and uncooked beans contain a poison called hemaglutin which is very toxic to birds.

This is not an all-inclusive list - there are likely other foods that we humans enjoy that are not so healthy for your pet. Perhaps the best advice is to limit human foods to rare treats if at all. After all, your beloved dog or cat did not evolve to eat what we eat - they are carnivores, and are designed to eat mainly raw meats and fats with occasional raw veggies. A more appropriate treat for Fido the pooch is a lump of raw beef or a knuckle bone and Fluffy the cat would be better with a raw chicken or turkey giblet...

References and resources:

Canine renal pathology associated with grape or raisin ingestion: 10 cases. J Vet Diagn Invest 17:223Ė231 (2005)

ASPCA Animal Poison Control Center:


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