Seri Robinson, a professor of wood anatomy, agrees with the marketers of "food-safe" finishes that bacteria-especially salmonella, listeria, and E. coli-are a threat to human health. But, Robinson says, those finishes can undermine the natural antimicrobial properties of wood. If an unfinished wooden cutting board or spoon is rinsed after use and allowed to dry on all sides, the drying action will pull bacteria deep into the wood, where it will be trapped and die. A finish will keep bacteria close to the surface, where it will multiply.