Dip your makeup brushes in rubbing alcohol once a week. Or better yet, dip your makeup brushes in tea tree oil! Get a cup of water, put ten drops of tea tree oil, and then place your makeup brushes in the mixture for 5 minutes. After that, place your wet makeup brushes on a clean, dry towel or napkin. Tea tree oil is a natural disinfectant that helps prevent acne. Your brushes will smell like tea tree oil for a while, but it'll keep it clean.
You can also use baby shampoo and apple cider vinegar!
Have a great Monday!