Most pet owners know that chocolate is toxic for their dogs and cats. It contains a chemical called theobromine which their bodies cannot metabolise, and causes vomiting, nausea, seizures and even death.
It was another common household food item that dumbfounded marketing manager Patrick Lim, 39. He says: "Grapes were my favourite fruit and I would occasionally share them with my Maltese, Jewel."
Then one day he noticed her stomach was bloated, and took her to the vet, who told him that the six-year-old dog had developed liver cancer. This was unusual for a breed which typically lives 12 to 15 years.
When the vet questioned Mr Lim about Jewel's habits and diet, he mentioned their shared grapes. "I was told that grapes are toxic to dogs. I was shocked. I had been giving her grapes on and off for six years, and they speculated that the grapes could have been part of the cause of the cancer."
When ingested by dogs and, to a lesser degree, by cats, grapes and raisins cause vomiting and nausea in minor cases and renal failure and death in the worst situations.
However, numerous American veterinary studies which have been conducted on the cause of grape toxicity in pets have been inconclusive. Unlike with chocolate, veterinarians have been unable to identify the element in grapes which causes the problems.
Jewel died eight years ago.
Now Mr Lim is very careful about what he feeds his eight- and nine-year-old schnauzers, Cleo and Clover. He says: "I feed them only fresh food, like boiled chicken and broccoli... I'm much more conscious about what is toxic to them."