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Onion Poisoning, a Pubmed search


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Onion toxicity. Apparently, onions cause haemolytic anaemia in dogs. From a search in Pubmed using the search terms " anaemia onions " the following 20-odd results were found:


In the period 1952 - 1953, in six published papers, an Italian researcher, C.Nardio, noted an association between onions in the diet and anaemia and blood changes in humans, rabbits and dogs.


In 1976, a Canadian Veterinary Journal reported a case of onion-related anaemia in a single dog, and the next year the same journal published a report on anaemia in cattle, again due to onions.


In 1979, an American Journal reported a similar case in Sheep, and in 1980, a Dutch report on a similar problem in a horse.


Six years later, dogs fed experimentally with dried onions were reported to show transient changes to their blood cells, and Dutch workers reported "Onion poisoning in cattle".


In 1992, the effects of onion diet and changes in the blood of cattle was again published, and the following year

a review article on Heinz body formation in dogs exhumed some of the previously published data.


Five years after, in 1998, a researcher called O. Yamato, in a paper called, intriguingly, "Induction of onion-induced haemolytic anaemia in dogs with sodium n-propylthiosulphate." stated:


"The haemolytic effect of sodium n-propylthiosulphate, which had been isolated from boiled onions, was studied to determine whether it could be one of the agents responsible for induced haemolytic anaemia in dogs. The oral administration of 500 mumol/kg bodyweight of the compound to dogs resulted in a haemolytic anaemia associated with an increase of Heinz body formation in erythrocytes, which was more severe in dogs with the hereditary condition which results in erythrocytes with high concentrations of reduced glutathione and potassium than in normal dogs. In the affected dogs there was a 10-fold increase in the concentration of oxidised glutathione in their erythrocytes 12 hours after the administration of the compound, whereas in normal dogs there was almost no change."


This groundbreaking work was followed within a few months by a paper where adult cats were fed human baby food with and without onions which resulted in the warning:


"CLINICAL IMPLICATIONS: Baby food or other foods containing similar amounts of onion powder should be avoided for use in cats because of Heinz body formation and the potential for development of anemia, particularly with high food intake. Cats with diseases associated with oxidative stress may develop additive hemoglobin damage when fed baby food containing onion powder."


In 1999, a herd of cattle were poisoned by onions in Canada, and Yamato published 2 more papers, on sheep and onions, and this time on dog blood samples with reduced glutathione levels.


In 2000, a report on a herd of sheep fed exclusively on onions was published. Why on earth would anyone want to feed their sheep exclusively on onions??? Why not mint? However, they reported:


"on the basis of this study it appears that pregnant ewes may be fed a pure onion diet with minimal detrimental effects."


For the most recent three papers on the subject I have copied their pubmed entries in full


Crespo R, Chin RP.

Effect of feeding green onions (Allium ascalonicum) to White Chinese geese (Threskiornis spinicollis).

J Vet Diagn Invest. 2004 Jul;16(4):321-5.

PMID: 15305744 [PubMed - indexed for MEDLINE]


Chang HS, Yamato O, Sakai Y, Yamasaki M, Maede Y.

Acceleration of superoxide generation in polymorphonuclear leukocytes and inhibition of platelet aggregation by alk(en)yl thiosulfates derived from onion and garlic in dogs and humans.

Prostaglandins Leukot Essent Fatty Acids. 2004 Jan;70(1):77-83.

PMID: 14643182 [PubMed - indexed for MEDLINE]


Munday R, Munday JS, Munday CM.

Comparative effects of mono-, di-, tri-, and tetrasulfides derived from plants of the Allium family: redox cycling in vitro and hemolytic activity and Phase 2 enzyme induction in vivo.

Free Radic Biol Med. 2003 May 1;34(9):1200-11.

PMID: 12706500 [PubMed - indexed for MEDLINE]


The overall thrust is that onions disagree with some individuals, humans and dogs included, and they can be toxic, if fed exclusively to cattle and horses, but not to sheep, apparently. Onions also are protective against cancer.


However, most dogs and people are not going to be poisoned by eating moderate amounts of onions, on a day-to day basis.


Perhaps someone on the boards would like to have a laugh by finding the scientific evidence that grapes or chocolate are the deadly poison that seems to be entering the consciousness of the dog loving public?

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Perhaps someone on the boards would like to have a laugh by finding the scientific evidence that grapes or chocolate are the deadly poison that seems to be entering the consciousness of the dog loving public?
It's been done, barely two weeks ago (scroll down a bit and there are a few citations):




No need to be smug. Animals, including humans, vary in their reactions to different substances. Some substances are more likely than others to provoke reactions in some animals. For dogs, chocolate, grapes, and onions are among the substances that happen to fall in that category.


Reports of single instances of adverse reactions are meant to alert others (vets, in the case of the articles you cited) of the possibility of seeing a reaction. When the reports start to pile up, then it's time to initiate a clinical study, and then (maybe) we get definitive statements about the probability of an average individual producing the reaction at a specified level of exposure. If people want to interpret the former as the latter, that's their prerogative. Caveat lector.

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There is a substance in chocolate that dogs are sensitive to. Theobromine varies in effect depending on how sensitive the dog is to the chemical. How much theobromine the dog is exposed to depends on the type and quality of the chocolate (high quality dark chocolate has a bunch, "white chocolate" has none), and of course how much is ingested compared to how much the dog weighs.


Here's the symptoms of theobromine poisoning:




Urinary Incontinence


Rapid Breathing and Heart Rate

Muscle Tremors




And, you feed onions to sheep if that's what you've got! I imagine they are similiar to turnips or parsnips in nutritional value.

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Perhaps someone on the boards would like to have a laugh by finding the scientific evidence that grapes or chocolate are the deadly poison that seems to be entering the consciousness of the dog loving public?


You may not find recent scientific studies on chocolate (theobromine) in PubMed since it's fairly well established fact.

Theobromine is found in chocolate, cocoa beans, baker?s chocolate, cola and tea and is believed to be the toxic component of chocolate. Baking chocolate is the most concentrated form of theobromine containing approximately 390 mg/oz versus 44 mg/oz found in milk chocolate. It is readily absorbed orally and widely distributed throughout the body. Theobromine is metabolized by the liver with primarily urinary excretion. In dogs, the LD50 for theobromine is approximately 250-500 mg/kg, however deaths have occurred following ingestion of 115 mg/kg. The half-life of theobromine is very long in dogs (17.5 hours) compared to other species. This may help to account for the susceptibility of canines to theobromine toxicity.
Source: Indiana Animal Disease Diagnostic Laboratory Spring 2000 Newsletter



Since grape seed extract (proanthocyanidin) is a fairly new "designer" neutraceutical these studies may be just begining.



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Does anyone remember the cocoa bean hull mulch scare? Does anyone still use that stuff? I don't actually, um, garden to speak of anymore, so I kind of lost track of that whole issue.

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I apologise if I have upset anyone, by being somewhat lighthearted at this time of the year, about some of the issues I raised into the toxicity issues with some foodstuffs.


Dogs (particularly beagles) have long been used as experimental animals to test the toxic properties of substances:

1/implicated in various human disease conditions, and

2/used as food additives/constituents for human foodstuffs.


As far as onions are concerned, the search points out that over 50-odd years, in only 24 published papers, there have been 2 anecdotal reports of onions affecting dogs, an identification of the causal agent, the mechanism of pathology, and the range of species in which an effect has been noted.


The experimentation has been performed on dogs, in vivo and vitro, and found that onion extracts or in the diet have a transient and minimal effect on dogs who are not predisposed to problems with handling some sulphur compounds in their blood.


Presumably, dogs who have this problem should not be given garlic either, since similar sulphur-containing chemicals are found in garlic, being a closely related Allium species.


Apparently, although this agent also affects some humans, by exactly the same mechanism as found in dogs, there is no cause for concern for humans, and the veterinary evidence for animals other than dogs says basically; don't let your cattle and horses feast exclusively on onions, although your sheep should probably be all right.


The causative agents of problems with grapes and raisins in dogs have not been defined. Substances with beneficial properties in grape seeds and skin have also been proposed, and have a synergistic action, affecting the stickiness of blood platelets in both dogs and humans. The rationale behind this is to define the heart-disease protective qualities found in grape products, particularly red wine, with a view to being able to market a product, a "neutraceutical" if you like (I don't like the term at all!), dietary supplement. However "neutraceutical" researchers are possibly a bit miffed if they can't feed their favourite lab animal grape products to excess without killing them prematurely.


Whether this is the whole story, no doubt time will tell, but there is still only anecdotal evidence regarding toxicity of onions or grapes for all dogs. I loved this abstract:


"Subchronic feeding study of grape colour extract in beagle dogs. Becci PJ, Hess FG, Gallo MA, Johnson WD, Babish JG.


The effect of feeding Welch's Special Grape Color Powder Type BW-AT at dose levels of 7.5 and 15% w/w in the diet for 90 days was studied in beagle dogs. Body-weight gain of male and female dogs at the high dose level was significantly decreased compared with control dogs. No other treatment-related effects were seen in food consumption, haematology, clinical chemistry, ophthalmology or gross and histopathological findings."


I.e. if you replace 15% weight for weight of a group of beagles diet for 90 days with extract of grape colour powder, they show a significant decrease in body weight gain! They were otherwise healthy (apart from the purple poo, no doubt!)


Doesn't seem too poisonous to those beagles, but no doubt they would prefer 100% dogfood, rather than 85% dogfood and 15% adulterant.


Dogs have also been poisoned by mycotoxins in cheese -


J Am Vet Med Assoc. 2003 Jan 1;222(1):52-3, 35.

Tremorgenic mycotoxin intoxication with penitrem A and roquefortine in two dogs. Young KL, Villar D, Carson TL, Ierman PM, Moore RA, Bottoff MR.


Ban feeding cheese to dogs! Just in case.


At the same time I do realise that a dog can quite easily gorge themselves on chocolate and that there is the potential for that to cause serious illness for a small animal. My 18 Kg BC would have to ingest 2070 mg Theobromine to reach the (low) 115 mg/kg toxic dose indicated, which would be 47.05 oz (almost 3 pounds of milk chocolate!) or 5.3 oz of premium baking chocolate - maybe a big problem if you are careless with your brownie mix, I guess.


The best course of action is not to leave treats or food of any kind where your pets can help themselves. But, to broadly demonise certain commonly available foodstuffs on the basis of a very few anecdotal poisonings by excess is simply scaremongering of the tabloid newspaper variety.


Merry Christmas to you all, but hide the chocolates from the dogs!

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Definitely hide the chocolates. This is a time of year when people put presents under the tree, not realizing they contain chocolate, but it's pretty obvious to a dog!


"Hey, look, they put this down here right where I can reach it - and covered it with this fun shiny crinkly stuff too!"


We almost lost a dog (actually my inlaws' dog) to chocolate poisoning when that exact thing happened. He really didn't eat that much in terms of theobromine (just a few chocolate truffles) but he went into shock. Christmas Eve at the emergency clinic is a hoot and a half, let me tell you. They said he was a little more sensitive than most dogs, just as some people are more sensitive to bee sting, spider bite, or snake venom.


Christmas time is really not the time to find out whether you have one of those dogs that is more sensitive to theobromine.


I feed all kinds of stuff to my dogs (I make their food) so I'm certainly not paranoid. But one should really be aware that dogs aren't EXACTLY like us and it pays to research a food item thoroughly, including discussing it with your vet, if you plan to make that food a regular part of your dog's diet.

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If people want to interpret the former as the latter, that's their prerogative. Caveat lector.
This is true -- but a lot of people don't understand how to interpret research findings. The press feeds into this confusion when they report that "grapes poison dogs" without putting the information in proper context. The Internet facilitates the spread of peoples' (possibly) distorted perceptions of reality. IMHO, the "overreaction" is not surprising.



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I asked a question a couple of days ago, about food toxicity in canines. Wow, all this response and I'm still confused. I guess I'm just dense. Baby likes garlic, jalape?o (in moderation), and cumin, because I eat those things.I feed her "nutricionally balenced" dog food but add the flavors I like., is this bad? :confused:

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I guess it could be bad, depending upon the amount and the substance. Why add the spices if it's nutritionally balanced? Find a food they like.


But to be quite honest, I give my dogs occasional "people food," including foods containing the same spices you mention. And everytime one of these conversations come up I think of all the things my dogs eat (that I never would) and how horrified many people on this list would be -- left over sheep parts and blood from slaughter, sometimes days old; rodents; sheep, horse and duck poop; blackberries and plants, etc. Then again, I don't give them things like Tylenol, chocolate, etc. So clearly dogs are different than people. I guess common sense is in order . . .


Did this muddy the waters anymore?



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You made me laugh (perhaps unintentionally) by saying, "I ,um, don't really garden anymore."


I really laughed thinking of a Border Collie's idea of gardening. It is more fun playing with my dogs and working sheep than gardening. Sheep eat the grass, right? Now need to mow, grow a few flowers, a few weeds, enjoy nature. Merry Christmas!


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Baby is NOT Morris the cat, but you can see the differance if her food smells like Daddy. DON'T offer her Polska Kielbasa unless you mean it. ROFL

Hunger is the best sauce

Escofier (sp?)

If thats true we'll have ours with very little sauce

Harry & Baby

Fleas Navidad

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Very interesting thread. I might add my two cents worth about Onions and other food toxins. Here at the vet school we get allot of the emergencies especially on the weekends. I have heard we have had raisin toxicity. And also Chocolate. And for my own personal experience it was my cat with Chronic Kidney disease who was ADR, so I brought him in. His kidney values weren't very high considering how long he has been diagnosed with this. But he did have Heinz bodies. They said it was interesting and that onions have been known to cause it, did he get into any onion products. I then thought of the Chicken dinner baby food I had given him on his Kd as he wasn't eating well.

I went home and checked the label and it was almost last on the list, :rolleyes: but there was onion powder in the baby food. Subsequent blood tests have proven much better and he is feeling pretty chipper at almost 17 years of age. So this post made me sit up and take notice for sure. Percy must be sensitive none of my animals will ever get any baby food or any other people food with out careful scrutiny of the labels.


As for feeding sheep or cows, onions. I used to work at a feed testing laboratory. And we tested all kinds of feed. Silage, corn, wheat,milo,soybeans, soy bean hulls, whole cotton seed, and other seeds whole and their shells. sunflower seed were hulls only as they could market the kernels. We also tested batches of Campbell's soup, milk, and yes onions on several occasions. All this was for protein,fiber,fat, moisture etc. Content. We even tested hard candy, and various weeds. This was all going to be plugged in to some feed formula to make cattle food mostly. This where the boxcars full of bakery prodcuts get incorperated in to feed, along with hot dogs and other interesting stuff.

Andrea D.

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Oooh, hot dogs are not supposed to be fed to ruminants! Pig feed maybe?


I've been really busy so didn't see your response, Caroline. I meant to be humorous. Besides the dogs, the farm, and homeschooling my five-year-old, my garden last year fell victim to twelve of these little beauties.




But, we do have the nicest eggs. With the price of eggs these days, the loss of the garden is a reasonable tradeoff. Next year, we WILL set up and area just for them, however.

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Here's some grape/raisin info I found on the ASPCA Animal Poison Control Center website (the data base is source of information I trust). While they note that the source of the poison in grapes is not known the data base is showing a consistent trend in kindey failure in dogs that show toxicity towards grapes/raisins. I wouldn't be surprised if it is determined via research that there is a gene that makes dogs unable to process a chemical in grapes/raisins that leads to kindey damage, where some dogs have this gene while others do not.



Enter the APCC AnToxTM database, a computerized system that contains nearly 500,000 animal-related medical conditions and that enables veterinarians to quickly identify toxic-substance exposures, recognize clinical signs and administer proper treatment. By tracking cases in this registry, similarities in animal medical conditions nationwide can be logged and syndromes can be identified.


Around 1989, the APCC began noticing a trend in dogs who had eaten grapes or raisins: Nearly all developed acute renal (kidney) failure. As more cases were reported, enough data was generated in the database to help veterinarians identify and treat dogs at risk. In all of the cases, the ingredients for potential acute renal failure were the same. Whether the ingested grapes were purchased fresh from grocery stores or grown in private yards didn't seem to matter, nor did the brand eaten. And the ingested amounts varied considerably, from over a pound of grapes to as little as a single serving of raisins. The cases weren't from any specific region, but instead came from across the United States.


The database showed that dogs who ate the grapes and raisins typically vomited within a few hours of ingestion. Most of the time, partially digested grapes and raisins could be seen in the vomit, fecal material, or both. At this point, some dogs would stop eating (anorexia), and develop diarrhea. The dogs often became quiet and lethargic, and showed signs of abdominal pain. These clinical signs lasted for several days -- sometimes even weeks.


When medical care was sought, blood chemistry panels showed consistent patterns. Hypercalcemia (elevated blood calcium levels) was frequently present, as well as elevated levels of blood urea nitrogen, creatinine and phosphorous (substances that reflect kidney function). These chemistries began to increase anywhere from 24 hours to several days after the dogs ate the fruit. As the kidney damage developed, the dogs would produce little urine. When they could no longer produce urine, death occurred. In some cases, dogs who received timely veterinary care still had to be euthanized.


Why did the fruit cause the dogs to become ill? No one knows. Suspect grapes and raisins have been screened for various pesticides, heavy metals (such as zinc or lead), and mycotoxins (fungal contaminants) and so far, all results have come back negative. In the cases where the grapes were grown in private yards, owners confirmed that no insecticides, fertilizers or antifungals had been used on the fruit.

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As many of my fellow parents know, entire school systems are currently disallowing certain "food" substances like peanuts. Our town in NH (a state notorious for the failings of its public education system) has found within itself the resources to entirely ban peanuts from its elementary school even though it won't identify my son's moderate learning disability because it "can't justify the cost".


The reason for the peanut ban? One little girl with an allergic response to peanuts. While most of the children in the school are not allergic to peanuts and some of the children in the school are mildly allergic to peanuts, this particular child according to her doctors, will certainly go into anaphillactic (sp?) shock if she comes in contact with the tiniest amount of peanut in any of its myriad forms.


My point is that just as humans vary greatly between individuals with regard to allergies and immune responses, dogs' allergic/immune responses are probably to some extent species specific, but more importantly with regard to subsatances like onions the allergic/immune response varies greatly between individuals. So, it seems likely to me that one Jack Russell might die from an allergic response to a small amount of onions whereas another might scarf down a whole Vidalia with no negative effects.


It might be of interest to folks that I knew a woman who had a terrier that demonstrated onion poisoning (as expressed by an attack of severe hemolytic anemia). Somehow the dog survived after thousands of dollars were spent on his veterinary care. It was generally made known that he had onion poisoning.


Several years later, a young stud dog to whom I had bred two of my brood bitches died of hemolytic anemia. His owner made use of the most advanced medical techniques to save him but after the dog had for all intents and purposes "died" twice and been resucitated, the owner let him go after a third crash. This dog was a close relative of the dog who had survived "onion poisoning."


Now, I don't necassarily discount onions as a contributing factor in hemolytic anemia, but I do believe that hemolytic anemia is very likely a medical cataclysm that is probably a result of an existing predisposition in individual lines of dogs. Vaccinations, tick born substances and microbes, parasite control agents and yes even onions seem to coalesce in the recent health history of dogs that have severe attacks of hemolytic anemia. I think the same is probably true of severe allergic responses to all sorts of substances.

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