The reason's simple; given the opportunity dogs are great scavengers, they will eat almost anything so are classed as omnivores - yes, a bit like us. Cats on the other hand are what are called obligate carnivores, which means they have no choice but to eat high protein foods, a few fats, but cannot digest carbohydrates properly. So they are choosy about what they eat and thereby ignore the dietary hazards so common to dogs at this time.
We all know the list of foods, delicious to us, which in variable quantities can be injurious or even fatal to dogs. Some of the deleterious mechanism and effects remain mysterious, like those of the dried vine fruits - sultanas, raisins and currants. There are suggestions they can be contaminated by fungi which produce toxins that survive cooking such that feeding them in puddings and cakes can poison.
Chocolate has been know about for ages; the risk is greater the higher the concentration of cocoa solids, such that the darker varieties present the highest risk.
Other hazardous food elements are onions and garlic, nuts - especially the Macadamia variety, but also in excess Brazil, almonds, cob and others (strictly not nuts) like peanuts, especially with salt and sugar coatings, and cashews.
All can fail the digestion test causing gastro-intestinal signs and even obstructions.
Indeed the list is limitless depending on quantities eaten, the added ingredients, the weight and size of the dog and its individual sensitivity to alien elements.
Vets see a lot of cases over the festive period and not all signs are conveniently 'pigeon-holed' into the above categories. Maybe the best way to look at Christmas food hazards is to look through the vets' day book.
Most of the problems seen are to do with what we throw away - or maybe think we have thrown away safely but that's far from reality. I have seen a repetitive assortment of emergencies involving the following:
The foil and string outer to cooking the Christmas bird is a huge temptation for the serial rubbish raider, either single-pawed attacking the bin or following Mr Fox's attentions to it overnight. The bones, bacon, mustard, skin, fats, juices, aluminium foil and string act like a 'Dyno-Rod' on the stomach and intestinal linings or at worst present a fatal toxic and obstructive combination on Boxing Day.
The meat juices may be erroneously seen to be both a tasty treat and nutritious to boot. But current bird or sausage meat preparation prior to the cooking process means both flavour enhancers, preservatives and injurious ionic salts taken in quantity can harmfully affect digestion and, longer term brain, liver and kidney functions.
The festive event may be over, but the temptations aren't. Not all the icing and marzipan has been finished; the chocolate and cream-filled profiterole pyramid leans drunkenly; the alcohol-soaked pudding scraps give up tempting aromas; and the decorative sweets still hang from the tree. All manifest huge sugar-burst-calories to wind up the hyper-excitable types - and not just the dogs!