Wiktionary
a. Describing any of various products that are impregnated with a substance that releases an odour when scratched
Wikipedia
The first generation of Scratch and Sniff was basically an aromatic scent of "perfume" with a coat of varnish over the substrate to dry. Scratching the printed piece released the fragrance and only last a few hours or days at most. 3M invented the technology in 1965, using a process originally developed for carbonless copy paper called microencapsulation.
Scratch and sniff technology generally refers to stickers or cardboard items that have been treated with a fragrant coating. When scratched, the coating releases an odor that is normally related to the image displayed under the coating. The technology has been used on a variety of surfaces from stickers to compact discs. Scratch and Sniff Publishing produces books with smell. Smell is integral to the storyline development using small hotspots with Micro-encapsulated inks.
Usage examples of "scratch and sniff".
Dana had been wakened by three of them soon after dawn, as they wandered in to scratch and sniff at the interesting new female scent.