The correct answer is - Increased use of hygiene products and a mostly indoor lifestyle leaves us with untrained immune systems.
Explanation:
Hygiene hypothesis states that the exposure to the microorganisms at the early childhood protects them from allergic reactions. This also boost the natural immune system of the organism.
The hygienic product is beneficial for the organisms. But its excess use and indoor lifestyle will prevent the exposure of the individual with the pathogens. The individual's immune system will not get time to prepare it and natural immunity is least present in these individual. These individuals are more prone to disease.
