"You should not flat iron natural hair more than once a month, especially if your hair is color-treated or damaged," says Powell. "Even once a month can be considered pushing it, so if you are flat ironing that frequently, it’s important that you are hyper-aware of your hair’s health." A good rule of thumb is to consider what your hair has been through—if it's been colored, or chemically straightened recently, it's probably more than a little damaged. Therefore, It's not recommended you apply any direct heat to your hair.