When Professor Rob Knight was growing up in Dunedin in the 1970’s and 80’s, parents didn’t typically worry about kids getting dirty and didn’t lather them in anti-bacterial gel either. Now we are learning more about more about the upsides of good bacteria thanks to work by Dr Knight who is and the co-founder of the American Gut Project and The Earth Microbiome Project. How clean is too clean can be confusing for parents and Knight and his co author try to answer questions about health and hygiene in their new book, Dirt is Good: The Advantage of Germs for Your Child’s Developing Immune System.