Honestly, we don't take the time to always wash our brushes but we should.
thoroughly clean your hairbrush at least once a month. The more styling products you use, the more frequently you should clean your brush, as it accumulates lots of hair and products.
All this accumulation will create residue, dead skin cells, and oil build up in your brush and can create bacteria and yeast, which isn't good and can have an unpleasant smell.
We love the Denman brush and the ones similar to it. the proper way to clean these brushes is to remove the bristle pad weekly to let the inside of the brush breath and dry.
So on your next wash day don't forget to also Wash your hairbrush.