rancidity: the state of being rancid; having a rancid scent or flavor (as of old cooking oil)
decay: an inferior state resulting from the process of decaying
mucus: protective secretion of the mucus membranes; in the gut it lubricates the passage of food and protects the epithelial cells; in the nose and throat and lungs it can make it difficult for bacteria to penetrate the body through the epithelium