When that same person is exposed to chickenpox again, the immune system will trigger the release of the particular chickenpox antibodies to fight the disease. When the immune system does not function properly, it leaves the body susceptible to an array of diseases. Allergies and hypersensitivity to certain substances are considered immune system disorders. In addition, the immune system plays a role in the rejection process of transplanted organs or tissue. Viruses and bacteria cause the majority of infections.
Viruses cause most colds, flu, coughs, and sore throats.
Bacteria cause most ear and sinus infections, strep throat, and urinary tract infections. Both bacteria and viruses can enter the body in many ways, including through inhalation, food, sexual contact, and skin contact. Antibiotics can be used to treat bacterial infections. However, antibiotics are ineffective in treating virus-related illnesses. In addition, antibiotics treat specific bacteria and overuse or misuse of antibiotics can lead to drug-resistant bacteria.