scientists studying the human voice system say, jokingly, that your vocal cords are located in the worst place possible: between the esophagus and the windpipe. As a result, it may be affected by acids ascending from the esophagus, or by phlegm flowing down from the upper and lower respiratory system.

In addition, since the larynx is so close to our air intakes, namely the mouth and nose, harmful microorganisms entering the body can easily affect it. Your vocal system can also be affected by chronic or acute inflammatory conditions. These can result from not only microorganisms, but also allergies and acid and inflammation-triggering diet, such as excessive consumption of animal proteins, as well as overstraining or improper use of your vocal cords.  All these might harm the natural immunity of your vocal cords, and result in lesions.