Avid Bella readers may recall that mascara is the first makeup to spoil. But my ever curious (and frugal) side wondered . . . why does it have to be my pricey DiorShow that gets the curse of the short shelf life?! Since the idea of bacteria near my eye doesn't apply to the reasonable realist in me, I figured if I knew why it went bad, I'd better understand when to toss.

Turns out mascara is more prone to the harboring of bacteria because of the way it's used – first you pull the wand out, then you put it back in. Think about those of you who reapply, or never leave the house without at least three coats. (You know who you are.) Each time you do that air gets into the tube.

If I haven't scared you off yet, find out what happens next read more.

Not only can "pumping" mascara cause it to dry out faster, that addition of air creates a veritable breeding ground. Each application introduces bacteria to the wand and pushes it into the tube. As you do so, both the (potential) bacteria and air inside are increased and trapped, and thus begins the reproduction. Gross already but then the relatively humid, closed environment becomes even more susceptible to bacterial growth (like closed toothbrush containers).

When pulling out the wand, make sure to do a twisting not pumping motion to minimize the trapped air for as long as possible. The good news is that mascara includes an antibacterial agent (commonly PVP or VP) to stave off this infection and keep you safe for a few months . . . after that, you may be sorry.

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