Until recently, most of us never thought twice before biting into a bar of chocolate or eating sweets. But most of us had never heard of a chemical called melamine, and how it had been added to some foods.
This chemical, used to make glue and plastics, was added to milk powder produced on the mainland to make it seem as if the milk had higher protein levels.
Until now, at least four babies have died and more than 50,000 been made ill by the contaminated milk powder. Countries around the world have banned chocolate and snacks, as well as dairy products manufactured on the mainland.
Many famous international brands, such as Cadbury, Lipton and Nestle, have found traces of the chemical in their products.
People are wondering what food is safe to eat. Experts say food makers should answer that question.
'Food manufacturing is an industry of conscience,' says Peter Cheung Chi-keung, professor of food and nutritional science at the Chinese University of Hong Kong. 'Only the manufacturers know where they get their ingredients, as food laws do not require the origins to be listed.'