Makeup brushes should be cleaned regularly to avoid bacteria, skin problems and pimples.
I have recently got sent a brush cleaner from www.beautybridge.com
It is the Glominerals Brush Cleaner.
This cleaner retails for $12, and is so worth it, for the 4oz bottle.
Just spray onto your brushes after each use, and wipe off onto a tissue. You will just see all the makeup come off. (It also has a really yummy smell)
I swear by this cleanser now. I use it every single day. Highly recommended!!