There seems to be a certain feeling of joy when you get your hands on a new lipstick or that mascara that makes your lashes look killer.

And to be honest, we don't really want to throw away our make-up until we scrape every last little bit out. Right?

Wrong. We should, because the truth is that everything we put on our face must be clean and fresh or else some nasty germs could clog up your beautiful complexion. UGH.

And if you haven't a clueee when you need to throw your make-up out, no worries. Grazia spoke to Bobbi Brown pro make-up artist Hannah Martin and she gave us all the inside scoop to when we need to clear out our make-up bags.

Once you open a product, liquid and cream based make-up "are best used within a year and powder products within two years."

But Hannah said to watch yourself with mascara as it's "one of the exceptions and really is at its best for the first two months and should be replaced after three months."

As a general rule, "longwear shadows and liners are also at their best for the first six months but powder products "such as face powder, bronzer, blush and eye shadow will last longer that liquid products," so they're good for a couple of years (if they last that long). 

The most important thing is to read the guidelines on the products and do regular clean-outs of your make-up bag and make-up brushes. You'll be sorted in no time!