Final answer:
Intact skin is the largest natural barrier to infection, acting as a protective physical barrier that prevents the entry of pathogens.
Step-by-step explanation:
The largest natural barrier to infection is intact skin.
Intact skin forms a physical barrier that prevents microbes from entering the body. It acts as a waterproof and protective barrier, preventing the entry of bacteria, viruses, and other pathogens. The skin also secretes oils and sweat that contain antimicrobial substances, further enhancing its protective function.
Learn more about Body's natural barriers to infection