NAC is an organic compound – a precursor of one of the major antioxidants, glutamine. It is widely used in medicine for dealing with the effects of Tylenol (acetaminophen) overdose, in cases of cystic fibrosis to loosen thick lung mucus and to help prevent altitude sickness. Uses have also been found for patients with blepharitis (dry, irritated eyes).
It is likely best to save this remedy for use when you first notice nasal congestion or start to cough. Take 500 mg three times daily until symptoms improve.