garlic, onions, grapes/raisins, and chocolate are all poison to cats and dogs

JJ, That is a great question. I wish I knew how to tell what was new product or not.

For myself, I am afraid of anything on the shelves right now. I just started home cooking for them. It was difficult to get them to try it, they are cats after all,  , but now they seem very happy with it!

Yes. Avocados can cause a number of problems due to their high fat content and other reasons.

The "Bad Food for Dogs" list is the best I've found to date, giving detailed explanations of just why the foods listed are bad:

http://mooreshaven.com/pets/dogs/safety/badfoodslist.html

Garlic isn't listed on there (although there's a mention of it in the Onion entry), probably because there's real controversy over garlic in pet foods and no clear answers yet.

There are documented benefits to garlic (and also undocumented ones that may or may not be actual benefits) ranging from flea and tick protection to immune boosting and even lowering blood sugar in diabetic dogs. But as has been pointed out garlic also contains thiosulphate, the compound in onions that causes hemolytic anemia in dogs (and cats -- and some primates, too).

Fortunately, Heinz-body hemolytic anemia has a fairly effective treatment: stop feeding onions and garlic! The damage to red blood cells will stop and the damaged cells will gradually be replaced by the body's natural healing abilities. But it's still a definite danger.

Here's one study you can read the abstract of:

http://avmajournals.avma.org/doi/abs/10.2460/ajvr.2000.61.1446

Short version: dogs fed garlic extract did develop Heinz-bodies in their blood cells (basically damage to the hemoglobin can lead to these "small round inclusions" in blood cells), but they did not develop clinical signs of hemolytic anemia. If enough red blood cells are damaged by Heinz-bodies, hemolytic anemia develops. (Hemolytic simply means "destructive to red blood cells.") They fed 1.25 ml of garlic extract per kg of dog (once each day for 7 days), which is roughly equivalent to 5 grams of whole garlic, which calculates out to about an ounce and a half of garlic per 22 lbs of dog.

Their conclusion was that garlic should not be fed to dogs.

My feeling is that garlic in moderation can be helpful, but I'm very careful about using it and I leave it out of any home-prepared pet food recipe that lists it as being "optional" (Pitcairn's recipes, for example).

I've seen various claims as to just how many cloves of garlic constitutes "moderation," with many people (including some holistic vets) claiming that it would have to be a lot of garlic to cause a problem -- up to 50 cloves (a whole bulb or more).

The number I've decided to trust is 1 clove of garlic per 20 lbs of dog per day, maximum. I feed much less than that (when I feed it at all). I also have large dogs (50 lbs and 85 lbs) so I've got a bit more leeway when it comes to toxicity levels of things like onions and garlic (and even chocolate -- our dog Barney, who we lost to a type of blood cancer five years go, once crunched up several shotglasses and ate a pound of dark chocolate "almond bark" in the same day - he'd burst the welding seams on his wire crate while we were out -- and survived unscathed!).

Why trust that number? Because it's one of the smaller numbers I've seen in discussions of just how much garlic would need to be eaten to reach toxic levels and while I'm not willing to give up on garlic completely (there seems to be real benefits) I also don't want to risk damaging my dogs' red blood cells. (I don't feed garlic to cats at all.)

Like a lot of health-related and pet-food related decisions, feeding garlic is a decision we each need to make for ourselves, after weighing health benefits and risks to the best of our ability. In the absence of solid research with definitive answers, we can only make the best decision we can with the knowledge we have at the time....

Department of Gastroenterology, Postgraduate Institute of Medical Education and Research

Information on the effect of garlic on the liver and optimal dose of garlic to avoid liver damage is not known.
This study was planned to determine the safe dose of garlic. Male wistar rats (110-170g) were fed fresh garlic homogenate (FSH) orally in three different doses (1.0, 2.5 and 5.0 g/kg body weight/day) daily for 28 days. Liver histology, serum transaminases, bilirubin and alkaline phosphatase were estimated at 0, 14, 21 and 28 days in control and experimental animals. 1.0, 2.5 and 5.0 g/kg body weight/day of garlic showed significant (P<0.001) deterioration in liver function tests (LFT's) after 21, 14 and 7 days respectively. A 1.0 g/kg body weight/day dose of garlic was associated with marked histological damage in liver after 21 days. Therefore, three lower doses of garlic (0.1, 0.25 and 0.5 g/kg body weight/day) were given orally to another group of similar rats to determine the safe dose of garlic. LFT's were serially measured and animals were sacrificed on the 29th day of experiment. All three lower doses showed significant deterioration in the LFT's values of animals after 28 days of feeding the freshly prepared garlic homogenate. Both doses of garlic i.e. 0.1 and 0.25 g/kg body weight/day were associated with normal histology of liver, but 0.5 g/kg body weight/day dose of garlic showed morphological changes in the liver of one animal. Therefore, the present study suggests that garlic with high dose has the potential ability to induce liver damage and low doses (0.1 or 0.25 g / kg body weight/day) are safe doses of garlic.

I understand that garlic is poisonous for dogs, but why is it often an ingredient in dog treats?
—Michelle S. http://www.aspca.org/site/PageServer?pagename=pro_apcc_ask_peoplefood&s_state=garlic

Good question, Michelle. Garlic does have toxic potential to pets, and is generally more potent than onion, also a member of the Allium species, in causing changes in red blood cells in dogs and cats. This is true in raw, cooked or powdered forms. In theory, "deodorized" garlic is allegedly less toxic, since the disulfides, responsible for both the odor and the toxicity, are usually largely removed.

Even at low levels of exposure to garlic, some change in red blood cells is likely; it is typically only when a significant number of red blood cells are altered that their oxygen-carrying capacity is noticeably compromised and clinical signs develop. Generally, it takes either a fairly large single ingestion or chronic exposure. These effects are also somewhat more likely to be seen in cats, as their red blood cells have shorter life spans and they're more likely to have bone marrow issues. However, the possibility exists that some dogs may also be genetically more susceptible to problems from garlic ingestions.

The lowest observed effect level in dogs in the scientific literature that we are aware of is 2.5 mg/kg of encapsulated garlic powder; slow heart rates and increased urination were seen. For comparison, a 20-pound dog consuming 1000 mg of garlic powder is exposed to a dose of 110 mg/kg.

The bottom line, Michelle, is that we do not definitively know at what dose any given dog may experience problems. An occasional low dose, such as those found in most commercial pet foods or treats, would not likely cause problems.  A conservative approach might be to avoid exposure to more concentrated garlic-based products.

For additional helpful information on pet poison prevention, please visit APCC online.

I stumbled across that a couple of weeks ago, and immediately bookmarked it myself. 

no garlic expert here either, but i have been giving it to my dog either raw, powdered (organic) or cooked for about the same length of time. not every day, just a few times a week depending on the meal. and i don't over do it either. she's 50lbs and seems fine on it. don't know if it's the diet, the garlic, the nutritional yeats or a combo, but she is also flea/tick/'skeeter free and on no chemicals. cats don't get garlic except on occasion that it's in something we are all eating. again, not over done in amount. my landlady feeds the ferals left over pasta meals (old school itialian 'hood) and they seem fine. 2 of my kities are from the backyard and were weaned onto her food before i got them. they still try and get to the sauce when i make it