This is a question I get asked a lot. And even when it is not said, I sometimes get the feeling that it's what's going through a persons mind when they look at my wooden eating spoons, say for example at a craft fair. While I have always thought that yes, they are just as hygienic as steel or plastic, this very question has been addressed by actual scientists with PhDs and Professorships and everything. How convenient.
Bacterial Growth Study
The interesting thing about this study is that it was commissioned by the U.S. Department of Agriculture when it realized that it had no evidence to support its official recommendation that plastic chopping boards be used instead of wooden ones in American home kitchens. Part of its original purpose was to see if there was a way to clean wooden chopping boards that would make them almost as hygienic as plastic boards. Not only did it not confirm their presumption that plastic was more hygienic, it showed that they were completely and totally wrong. Dr Dean O. Cliver, Professor of Food Safety at the University of California carried out a comparison of bacterial growth on wooden versus plastic chopping boards (read full article here).
He concluded that wooden surfaces were resistant to bacterial growth and were much more hygienic than plastic surfaces, especially with use:
"(Disease bacteria)... were not recoverable from wooden surfaces in a short time after they were applied, unless very large numbers were used. New plastic surfaces allowed the bacteria to persist, but were easily cleaned and disinfected. However, wooden boards that had been used and had many knife cuts acted almost the same as new wood, whereas plastic surfaces that were knife-scarred were impossible to clean and disinfect manually"Conclusion
From my perspective, having lightly studied the cellular structure of wood, this makes perfect sense. Wood is made up of biological cells. It has evolved to resist bacterial and fungal growth and therefore rot. The heartwood of living trees is actually dead but the structure of the cells still imparts resistance which plays an important role in keeping trees from falling over! Also, plastic is commonly used in biological wastewater treatment systems as a substrate for microbes because it just happens to be the perfect thing for them to grow on. So there you have it: Yes, wooden kitchenware such as spoons, bowls and chopping boards are hygienic!