n-acetylcysteine increases glutathione levels supplementation exercise performance and reduces oxidative stress only in individuals with low of NAC (N-Acetyl L-Cysteine)

I see a lot of info online that says they are safe

Braun, Fresenius Kabi, ICU Medical, Cardinal Health Types: 0.9% Sodium Chloride (Normal Saline), 5% Dextrose (D5W), Lactated Ringers (LR), Dextrose in Saline, Half-Normal Saline (0.45% NaCl), Multi-Electrolyte Solutions, Sterile Water Strengths/Volumes: 50 mL, 100 mL, 250 mL, 500 mL, 1 liter

Low glutathione levels are associated with weakened immune function

It is a copolymer of ethylene and propylene

Concentrations typically used in cell culture range from 10 ng/mL for sensitive signaling assays to 100 ng/mL for full receptor saturation studies

Lessons for COVID-19 Immunity from Other Coronavirus Infections