Chocolate contains Theobromine (a compound related to caffeine), that is toxic to dogs in sufficient quantities. Humans can break down and excrete Theobromine much more efficiently compared with dogs, and therefore thankfully can eat large amounts of chocolate with no ill effects! Cocoa powder and cooking chocolate are the most toxic forms as they can contain 10 times more Theobromine compared with milk chocolate. A 10kg dog can be seriously affected if it eats a quarter of a 250gm packet of cocoa powder, or half of a 250gm block of cooking chocolate. Thus, a chocolate mud cake could be a real health risk for a small dog and even licking a substantial part of the chocolate icing from a cake can make a dog unwell. Dark chocolate is the next most dangerous form, with milk chocolate being the least dangerous. A dog generally needs to eat more than a 250gm block of milk chocolate to be affected with often only minor clinical signs. Obviously, the smaller the dog, the less it needs to eat. My advice however, is to never use chocolate as a treat to ensure they do not get a taste for it and seek it out! Xanthines affect the nervous system, cardiovascular system and peripheral nerves, plus have a diuretic effect as well.
Clinical signs we can see are:
There is no specific antidote for this poisoning. It is therefore imperative to seek veterinary advice and treatment after known ingestion. Vomiting should be induced in the first 1-2 hours if the quantity is unknown, and administering activated charcoal may inhibit absorption of the toxin. The rest of the treatment is symptomatic and may include anticonvulsant therapy if neurological signs are present, plus oxygen therapy, and intravenous medications and fluids to protect the heart. Milk chocolate will often cause diarrhoea 12-24 hours after ingestion which should be treated symptomatically (fluids, etc) to prevent dehydration.
Onions in any form (raw/cooked/dehydrated or powdered) can be life threatening to dogs. Toxic effects are consistently noticed if your dog consumes over 0.5% of their body weight eg a 10kg dog needs to eat 50g of onions to show clinical signs. Onions contain a product called Thiosulphate which dogs cannot digest. The Thiosulphate alters the red bloods cells weakening their cell membranes so the life span of the cell is reduced. If enough red blood cells are destroyed, the dog becomes anaemic and the body is starved of oxygen. The number of cells destroyed is dose dependent, but small amounts fed over a period of time can lead to problems due to a gradual reduction in red blood cells, and some dogs can develop very severe reactions after eating only a small amount. Clinical signs may occur in as little as 24 hours after ingestion but usually takes several days.
Clincal Signs we generally see are:
If ingestion is recent then inducing vomiting and administering charcoal tablets to reduce absorption, may be all that is needed. However, with more severe signs hospitalisation and a blood transfusion may be needed to save his/her life. In fact I’ve had to blood transfuse 2 dogs in the last couple of years with life threatening anaemia from eating cooked onions from the BBQ!! Best to avoid onions all together!
No one is totally clear about which component of the grapes or raisins makes them so dangerous to our dogs. Basically, grapes and raisins are poisonous, and problems have been seen with grapes at doses as low as 12 gram per kg of body weight. Raisins are more difficult to quantify, as it is thought that the toxic component is more concentrated, and therefore you may need far less of them to make your dog ill. However some dogs can ingest much larger doses and suffer no ill effects. The toxic component (not yet been identified) causes kidney failure which can be fatal.
Clinical signs of toxicity are usually seen within 24 hours of ingestion and include vomiting/diarrhoea, lethargy, reduced appetite and abdominal pain.
Treatment initially should be induction of vomiting and administration of activated charcoal to bind the toxin. This is followed by intravenous fluids to protect the kidneys and flush out the toxin. Your vet will need to monitor kidney function and urine production to ensure irreversible kidney damage has not occurred. I would strongly recommend not using grapes/raisins as treats as one study shows that 50% of affected dogs died!