There are no incurable diseases - only the lack of will. There are no worthless herbs - only the lack of knowledge (Avicenna). Antiviral, antibacterial and antifungal drugs have had a substantial impact on human health to cure infectious diseases. Although, various antibiotics are being used to control these diseases, using them for a long time can reveal bacteria which are resistant to some drugs causes clinical challenges in treatment of the infectious diseases. Hence, investigation on discovering new antimicrobial components, from some sources like plants, is important. Undoubtedly, using medicinal plants is the oldest way to treat the disease, and there has been a close relationship between humans and plants in the course of history. This book tries to introduce some essential oils of medicinal herbs healing effect on infectious diseases, bringing forward biologically active compounds isolated from plant species for the elimination of pathogenic microorganisms.