Most dermatologists will tell you to clean your tools, especially foundation and concealer brushes daily for peoples with sensitive skin , for the powder brush twice a week "minimum " to prevent product buildup. Because these brushes are used on your face , and Brushes that are used around the eyes should be cleaned at least twice a week.
Clean your makeup brushes regularly can extend the life of the bristles and make for better product application , If you have skin breakouts or infections, experts and dermatologists recommend washing all brushes daily.
How to clean your makeup brushes :
There are plenty of products specially designed to clean your brushes , or you can also do it yourself with warm water and either mild soap or shampoo.