In an article published on March 10 in Being too clean puts children at risk of allergies, autoimmune diseases A concept in immunology called “hygiene hypothesis” states that interactions with the microbial world – an environment full of bacteria, parasites, viruses and other microorganisms – after birth are extremely important for the proper development of the immune system. “The immune system is a learning device, and at birth it resembles a computer with hardware and software but few data. Additional data must be supplied during the first years of life, through contact with microorganisms from other humans and the natural environment,” according to a 2016 study cited by Bridle.