(a) Antiseptics — Antiseptics are mild chemical substance applied to the body to prevent its growth and kill germs. Example – Iodine and Lysol
(b) Disinfectants — These are the chemicals that kill microbes once they come in contact with them, they are too strong to be used on the body. Example – Phenol and Cresol
(c) Vaccines — They are the substances that are administered in the body to provide passive immunity. These are the materials that are germs or secreted by germs. Example – DTP, OPV