How does the human body use its own chemical defences to prevent infection

The body has its own chemicals that help enhance defense against infection caused by invasion of foreign entities or pathogens such as bacteria.

These chemicals are usually found within the innate or non - specific arm  of the immune system. These chemicals include- Hydrogen peroxide, nitric oxide and  chlorine free radicals. All these are found in neutrophils which are the second line of defense in innate immunity when pathogens have managed to breach the first line which includes the skin. Neutrophils are white blood cells that engulf bacteria and release their chemicals on its membrane, rupturing it and thus killing the bacteria.