A sneeze. A scratch. A tear. Typically, these reflexes barely register on your consciousness or, if they do, its as an annoyance. In reality, however, each is an unconscious action that, in its own way provides essential protection against disease causing microbes or toxins before they can do harm.
Scratching is a natural reaction to itching, which is triggered by tiny receptors in the skin’s nerve endings.
Coughing helps to clear mouth, throat and lung tissues of foreign invaders, such as moulds, pollen, dust mites and pet dander, as well as mucus laden with microbes. The irony of this is that many respiratory infections may be spread by droplets of pathogens put into the air by the cough.
Sneezing is like coughing but directed through the nose. We also sneeze to get ride of microbes that multiply in the nasal passageways, as the result of having cold.
Vomiting occurs when harmful substances in the stomach are identified by the receptors in the walls of the digestive tract.
Tearing keeps the surface of the eyes moist and sterile. Tears also protect the eye when dust or debris irritate it. Crying, a natural response to stress, flushes away certain harmful chemicals produced by anxiety.
Despite this impressive range of barriers, reflexes and chemicals, dangerous invaders do occasionally manage to penetrate the body.