Carlos Oliveira of Peterborough has found some great bargains at the dollar store: tissue paper, gift bags, tape. But he was concerned when his son received knock-off Play-Doh that had no manufacturer’s information on the packaging. He’s right to be cautious. Lorne Lipkus, a Toronto lawyer and anticounterfeiting expert, says some dollar stores can be filled with counterfeit products that pose a health and safety risk. Here’s what you need to know to protect yourself.