Prostaglandin

Scientists have learned how aspirin interferes with a protein enzyme. One form of the enzyme makes the prostaglandin that causes pain and swelling. Another form of the enzyme creates the protective kind of compound. So, while aspirin can reduce pain and swelling in damaged tissues, it also can harm the lining of the stomach and small intestine. Still, aspirin does things that other drugs for treating pain cannot do.

This enzyme generates an inflammatory mediator known as prostaglandin, which triggers pain and other aspects of inflammation.

Indeed, it’s possible to create the full storm of cold symptoms with no cold virus at all, but only a potent cocktail of the so-called inflammatory mediators that the body makes itself[,] among them, cytokines, kinins, prostaglandins and interleukins, powerful little chemical messengers that cause the blood vessels in the nose to dilate and leak, stimulate the secretion of mucus, activate sneeze and cough reflexes and set off pain in our nerve fibers.