Reapplying makeup with dirty brushes will only lead to a face full of bacteria. Yes, any makeup artist will tell you that brush-cleaning time is their least favorite part of their job. Remember to clean your brushes after each use. If you don't care about that dirty brushes can make you breakout, be informed that they will affect your makeup application. Would a painter use a dirty brush to paint your walls? Exactly. Not only will the colors muddle together, the bristles are already overloaded with product, blurring your perfect cut crease.