The hygiene hypothesis is a theory that proposes a connection between the rise of allergic and autoimmune diseases and modern lifestyles with reduced microbial exposure. The podcast episodes discuss how the gut microbiome, and its interaction with the immune system, may play a key role in this phenomenon.

In Episode 18974, Dr. Sarkis Mazmanian explains how the hygiene hypothesis relates to the rise of conditions like Parkinson's, autism, and depression, and how early-life microbial exposure can influence the development of the immune system and gut-brain axis. Similarly, Episode 64130 touches on the hygiene hypothesis and the connection between gut microbes and health, including personality and behavior.

The episodes highlight the importance of understanding the role of the microbiome in human health, and how microbiome-based therapeutics may hold promise for addressing a range of conditions.