When phlegm comes out when you caugh it is called productive cough. If nothing is produced it is called as dry or non - productive cough

A nonproductive cough is a cough that does not bring up phlegm or mucus. It is also called a dry cough, and tends to irritate the throat much more than a productive cough (a cough that brings up phlegm and/or mucus) does.

AntibioticS

"Productive", when speaking of coughs, means "productive of mucus." If you're hacking up balls of phlegm, that's a productive cough. Certain diseases are associated with productive coughs, and others aren't. Flu is one of the ones that aren't as mucus-producing in most people.

This is the mustard gas (C4H8Cl2S).