When it quenches a free radical, it becomes oxidized and cannot quench more free radicals until it is converted back to its reduced form by special enzymes
Anything that expects you to reuse or self-sterilize is trading your skin's safety for better margins
Bibcode:2011ToxAP.253..197A
Additional information FDA Disclaimer: The statements made regarding these products have not been evaluated by the U.S

20x more bio-available than NAC, NACET is clinically studied to boost glutathione levels by 300% NACET contains a sulphur-group, which aids in scavenging for free radicals, but also has a strong smell, so we added essential oils and vanillin Glutathione, the "Mother of all Antioxidants," decreases as we age which makes NACET the #1 way to increase cellular glutathione Product Details 20x more bio-available than NAC, NACET is clinically studied to boost glutathione levels by 300% NACET contains a sulphur-group, which aids in scavenging for free radicals, but also has a strong smell, so we added essential oils and vanillin Glutathione, the "Mother of all Antioxidants," decreases as we age which makes NACET the #1 way to increase cellular glutathione Nutri by Nature's Fusions delivers Neuro-NAC, a source of NACET (N-Acetyl L-Cysteine Ethyl Ester) which may help protect the body from free radicals
That assumption is untested