“Are we too clean” – an outdated concept or a concept in need of clarification?

This short commentary looks at how the concept that we are now “too clean for our own good” needs to be interpreted in relation to the growing understanding of how, and why, exposure to microbial “Old Friends” from our evolutionary past is essential for correct functioning of the human immune system. Without this exposure, this system can become over reactive which is a fundamental cause of allergic diseases such as asthma and hay fever, and other chronic inflammatory diseases such as Multiple Sclerosis, Type 2 Diabetes and Inflammatory Bowel Disease. Activities which are now being see as ways to restore our exposure to the right types of organisms including things like natural childbirth breastfeeding, family contact and more outdoor activity. It also looks at why cleanliness, as inferred in this context, must be clearly distinguished from hygiene (the measures which protect us from infectious disease agents).