N-Acetyl Cysteine (Nac) Is A Sulfur-Containing Amino Acid That Acts As A Stabilizer For The Formation Of Protein Structures, And Promotes The Formation Of Glutathione.* Glutathione Is A Powerful Free Radical Scavenging Compound That Also Helps To Maintain Normal, Balanced Immune System Function Quercetin Is A Naturally Occurring Free Radical Neutralizer That Supports Healthy Seasonal Immune System Function.* Laboratory Studies Have Demonstrated That Quercetin Can Also Help To Promote Normal Respiratory Function Zinc Has Been Included For Its Immune-Supporting Properties Gmp Quality Assured: Npa A-Rated Gmp Certification Means That Every Aspect Of The Now Manufacturing Process Has Been Examined, Including Our Laboratory/Testing Methods (For Stability, Potency, And Product Formulation) Packaged In The Usa By A Family Owned And Operated Company Since 1968 Now Supplements N-Acetyl Cysteine (Nac) Is A Stable Form Of The Non-Essential Amino Acid Cysteine. It Is A Sulfur-Containing Amino Acid That Acts As A Stabilizer For The Formation Of Protein Structures, And Promotes The Formation Of Glutathione.* Glutathione Is A Powerful Free Radical Scavenging Compound That Also Helps To Maintain Normal, Balanced Immune System Function.* Quercetin Is A Naturally Occurring Free Radical Neutralizer That Supports Healthy Seasonal Immune System Function.* Laboratory Studies Have Demonstrated That Quercetin Can Also Help To Promote Normal Respiratory Function.* Zinc Has Been Included For Its Immune-Supporting Properties