Just For Laughs Dr. Stinky's Scratch N Sniff Stickers Christmas Set 4-Pack (Christmas Tree, Gingerbread, Cutout Cookie, Candy Cane) 4-Pack- Christmas Tree, Gingerbread, Cutout Cookie, Candy Cane What enables Scratch-N-Sniff Stickers to last so long? Micro-encapsulation is a process where fragrance is captured into a tiny bubble. The bubble is then applied to paper during the printing process. Each microscopic bubble attaches to the fibers of the paper. Only when you scratch the sticker is the bubble broken and the scent released. By encapsulating each scent, the life of Scratch-N-Sniff stickers is drastically increased. The Stink Factory uses the highest quality inks, scented oils, and printing presses. All components for Dr. Stinky's Scratch-N-Sniff Stickers are made in North America. The Stink Factory performs extensive safety tests. In addition, we pride ourselves in selecting the highest quality scents and the best printing presses. Rest assured mom, Dr. Stinky's Scratch-N-Sniff Stickers are a safe way for kids to have fun. Excellent stocking stuffers!