Olive leaf extract is one of the most well known and studied natural remedies to fight pathogens. Its properties are attributed to its precious polyphenolic phytonutrient compound, known as oleuropain. A significant number of clinical studies suggest that oleuropain demonstrates antimicrobial and antibacterial properties, making it an excellent natural antibiotic without any side effects. It offers protection against a great range of viruses and bacteria of the upper respiratory tract, such as the common cold, pharyngitis, sinusitis and many more. It is suggested that oleuropain activates the immune system, and at the same time destroy pathogens and inhibits their proliferation.