Pet owners take great care to keep poisons out of reach of their pets: human medicines, pest control poisons (slug, rat, and mouse bait), and weedkillers are all kept in secure places. But there is one type of poisoning that can take pet owners by surprise: normal human foodstuffs. The metabolism of dogs and cats has unique enzyme pathways. Foods that present zero risk to humans can be highly toxic when consumed by pets.
Cats are less commonly poisoned than dogs: they’re more fastidious eaters. Dogs often have ravenous appetites, with no “off-switch”, so they are prone to eating large quantities of foods that can be bad for them.
Chocolate is the best example: it contains the stimulant theobromine which gives humans a pleasant buzz, but it’s highly toxic to pets, causing heart failure. The lethal dose can be as little as two ounces (50g) of dark chocolate for a 10kg dog, or twice this amount of milk chocolate. It’s never safe to presume that a dog that has eaten chocolate will be OK: it’s dangerous to “wait and see what happens”. If your dog has eaten a toxic dose, by the time they start to show signs of poisoning, it will be too late: little can be done to help them. Instead, if you know your dog has eaten chocolate, take immediate action.
First, work out exactly how much chocolate has been eaten, and of which type (the percentage of theobromine varies, with darker chocolate containing higher levels). Next, note the weight of your dog in kilograms. Then, go to an online chocolate poisoning calculator: enter the above details, and you will be given immediate advice on what action needs to be taken.
If in doubt, just phone your on-call vet for advice. If your dog has consumed a dangerous amount, you need to rush them to the vet at once, whatever the time of day or night: all vets are obliged to offer a 24-hour emergency service. The vet will give an injection which forces your pet to vomit, immediately emptying the stomach and removing the chocolate from their digestive system before it can be absorbed. Sometimes other treatments may be given, such as activated charcoal, an absorbent substance which can help to mop up any toxins further down the digestive tract. If a dog is forced to vomit within an hour of eating a toxin, like chocolate, this is usually enough to pre-empt a serious and life-threatening crisis from developing several hours later.
Xylitol is another substance that is surprisingly poisonous to pets. This is used as a sweetening agent to make toothpaste, chewing gum, and lozenges palatable to humans (it’s known as “E976″). Xylitol confuses the canine hormone system, fooling it into “thinking” that the blood sugar levels are high, leading to insulin release, with the blood sugar dropping precipitously as a result. Anything more than a small quantity can cause dogs to collapse. If your dog eats an occasional piece of chewing gum, don’t worry, but if they steal your stash (and they do sometimes), then a visit to the emergency vet is needed. As before, make a note of exactly which product was eaten (take a photo of the label to show the vet), and what time it happened. Again, online toxicity calculators can help you work out the level of risk.
Grapes and raisins are an important oddity: while perfectly safe for humans to eat, there have been cases of dogs suffering severe, fatal kidney failure after ingestion of relatively small amounts. The reason for this toxicity is not fully understood: it may be linked to some type of mould in some batches of grapes. This would explain why some dogs can eat high numbers of grapes without showing any sign of illness, while others can suffer extreme consequences after eating just a few grapes. The known risk of grape poisoning means that these days, many vets recommend that every dog that has eaten any quantity of grapes or raisins should be treated urgently to reduce the risk of kidney damage. Again, this starts with inducing vomiting to empty the stomach, removing the grapes from the system. In some cases, further measures such as intravenous fluids for 24 hours may be suggested, to protect the kidneys if a significant risk of damage is suspected.
Other human foods also present a risk of toxicity to pets, but they tend to only cause issues in unusual circumstances, such as pets that have a higher consumption than normal.
Onions, garlic, and salt are good examples: the small amounts used to flavour human meals are safe for pets, but if they ingest high quantities, (drinking onion soup or swallowing sea water, or eating pure onion-based takeaway meals) then they can get into trouble.
Coffee and tea contain dangerous stimulants but only if consumed in excess. Don’t let your dog dive into the carafe of iced coffee that you’ve prepared on a sunny day, but don’t worry if they have an occasional cup of tea. Avocado and macadamia nuts may be beloved by trendy millennials, but they contain chemicals that can harm pets if eaten in moderate quantities: they’re best avoided.
Raw yeast dough can swell up in the digestive tract, causing an obstruction: you’re unlikely to feed this to a pet deliberately, but do keep it out of reach.
Finally, alcohol can be poisonous to pets, and they are more sensitive than humans. A couple of measures of whisky would poison a 10kg dog.
Just because food and drinks are safe for you, you can't assume it's fine for your pet.