The immune system is the defense mechanism of the body, which is made up of cells, tissues, and organs that defend the body against any foreign attacks. The immune system protects the body against parasites, bacteria, viruses, and fungi that cause diseases and other defects. Your immune system can be termed as the second line of defense to human system aside from the physical defense mechanisms including the skin and the mucous membrane. This means that, when the immune system is attacked or becomes vulnerable, the human system falls victim to several diseases. This is when one may experience several frequent illnesses, slow recovery from ailments, fatigue, slow development, digestive disorders, and allergies.