My De-nude lipglass from Artificially Wild doesn't have the usual MAC scent. It smells so floral, almost like old, granny perfume. I tried it once a while back but couldn't wear it very long because the smell was nauseating. Is that what you'd mean by 'rancid'? If yes, then I'm throwing it away. I just took the smell to mean that this was a one-off problem. Hmm, this is all very interesting. Do you think maybe some lipglasses turn rancid faster than others because of something they use on certain colors and not others? I purchased lipglass from Sharon Osbourne collection, The Simpsons, and some from Playland but they've all been fine. The only dud that I got was De-nude from Artificially Wild and that scent was headache-inducing. Still, didn't keep me from throwing it away though because I just assumed that they used a different scent but that the general 'formula' was ok to use?