Initial Posting: 4/19/2015    Last Update: 8/3/2017
Answer: Although NAC has mucus-thinning properties when directly inhaled, there is little evidence that oral supplementation can reduce the thickness or volume of nasal congestion. More about this is found in the Review of NAC (N-Acetyl Cysteine) Supplements.
If you are suffering from nasal congestion due to a cold, taking a zinc lozenge may reduce the duration of nasal discharge and nasal congestion if taken within 24 hours of onset of symptoms.
Certain probiotics have also been shown to reduce the duration of cold symptoms such as a runny nose.