Pearlyn: New brushes from reputable brands should be safe, especially if they are protected with plastic caps or stored in sealed compacts. Once you start using them, be sure to cleanse them once a fortnight if you use them every day or at least once monthly if you hardly apply makeup.
Try Bobbi Brown’s Instant Brush Cleaning Spray or M.A.C’s Brush Cleanser. But using a mild shampoo works, too. I like "disinfecting" my brushes in a jar of makeup remover diluted with water (if it’s good enough for my skin, it’s good enough for my brushes!) for a few minutes.
Rinse thoroughly, squeeze off excess water with a clean towel and lay the brushes flat on the towel to dry – preferably in the sun. And since we’re on the subject of hygiene, always throw out your makeup sponges (they don’t cost a lot: you can buy 30 pieces in a bag for about $10 at pharmacies) every two to three weeks as bacteria breeds easily in these after they have been used on oily skin, especially!