The hygiene hypothesis is a hot topic among allergists and immunologists; it suggests that the prevalence of allergic diseases in modern societies is related to our overly hygienic lives. For example, kids who grow up on farms usually have lower rates of allergies and asthma. However, if a child stays indoors in a sterile environment all the time, then his immune system is never challenged and never has a chance to ‘learn’ what it should attack. Thus, the immune system overreacts to substances like pollen.

The Washington Post recently reported that Duke University researchers think that the appendix – long thought to be a vestigal organ – may serve an important function after all.

Appendectomies have been common throughout the history of modern medicine, and people live fine without an appendix, so it was thought that the organ was non-functional. It turns out that the appendix plays a role in the immune system by protecting good germs. The human body contains both bad bacteria (that cause illnesses) and good bacteria (that assist with bodily functions like digestion).

The appendix ‘acts as a good safe house for bacteria,’ says Dr. Bill Parker, study co-author. It's a bacteria factory that cultivates good germs. This is important because some conditions (like cholera) can kill off all the good bacteria in the gut. In such a case, the appendix can reboot the system.

In modern society, a ‘reboot’ is usually not necessary because if a person's good bacteria get killed off, it's very easy to pick up more good germs from other people. So, if you have an inflamed appendix (appendicitis), you should still have it removed. About 400 Americans die from appendicitis each year.

Dr. Parker says that the appendix may be another case of an overly hygienic society triggering an overreaction by the body's immune system.

Learn more about the hygiene hypothesis in the following interview:

Dr. Thomas A.E. Platts-Mills on Allergen Avoidance through Environmental Control