The select nutrients in this formula – Vitamin C, Vitamin D3, and Zinc – have been chosen for their synergistic ability to offer protection by supporting the body’s immune response.* Quercetin, Bromelain and Nettle Extract, which have been found to help promote healthy mucus viscosity and provide histamine support.* Additionally, N-Acetyl L-Cysteine (NAC) is included in this formula as a powerful free radical scavenger.* NAC is also an amino acid precursor to glutathione, one of the most important antioxidants in the body.*