“You have nighttime free radicals and daytime free radicals. Daytime free radicals are the sun and pollution, the nighttime free radicals are, um, I’m really not sure what those little boogers, the little nighttime pesticides, are that damage your skin at night, but they are there!”

Free radicals are destructive molecules that cannot tell time! Yes, it is true that sunlight is a major source of free radicals generated in the daytime, yet pollution, whether coming from auto exhaust or industrial pollutants, is ever-present. The level of pollutants may be higher during daylight hours, but it certainly doesn’t disappear when the sun goes down! And what about the fact that the oxygen we need to live is a potent source of free-radical damage, and that’s around all the time, too?

I don’t know what to make of the “nighttime pesticides” comment, but unless you are sleeping in a field or on farmland that has recently been crop-dusted, I wouldn’t be too concerned about pesticides on your skin at night.

Regardless of whether it’s day or night, antioxidants are state-of-the-art ingredients to look for when shopping for skin-care products, and there are dozens available (with no clear-cut “best” choice among them), but none of them can distinguish between daytime and nighttime free radicals. In theory, antioxidants in well-formulated skin-care products should perform regardless of the time of day.