Final answer:
The 'hygiene hypothesis' suggests that reduced exposure to pathogens in developed nations may lead to increased allergic and autoimmune conditions due to an immune system that is less trained and potentially develops abnormally.
Step-by-step explanation:
The question of whether the increased lack of exposure to pathogens in developed nations leads to reduced or abnormal immune responses is a complex one. Current evidence suggests that in environments with high levels of sanitation and reduced exposure to various pathogens, there can be a phenomenon known as the 'hygiene hypothesis.' This hypothesis suggests that less exposure to infectious agents and microorganisms in early childhood could potentially lead to an increase in allergic and autoimmune conditions, implying that the immune system may develop abnormally or not be as robust. While limited exposure to pathogens can lead to a reduced incidence of infectious diseases, it may also mean that the immune system is less trained to deal with a variety of threats, potentially leading to heightened sensitivity to non-pathogenic antigens, resulting in allergies and autoimmune diseases.