I've noticed this on books, paper packaging, and clothes — anything that will absorb an odor, basically. Is this some sort of chemical treatment they use in warehouses, or... ?
the odor people mostly associate with puke comes from butyric acid
Butyric acid is used in the preparation of various butyrate esters. It is used to produce cellulose acetate butyrate (CAB), which is used in a wide variety of tools, paints, and coatings, and is more resistant to degradation than cellulose acetate. CAB can degrade with exposure to heat and moisture, releasing butyric acid.
It is likely paper and cardboard thst has not gone through processes to remove smelly components. Likely some phenols or as the other commenter mentioned, butyrate. Cheap recycled paper and cardboard often has these smells, especially if it gets wet.
