“The dual process is a root whitening program, also known as a global program. This treatment should be done every three to four weeks or whenever you grow ½ inch,” says Paglionico. “This needs to be done more often because the bleach is applied directly to the scalp, which heats up the bleach and helps it develop faster.”

“If you wait too long, the temperature will drop and the hair may not be as light as when you last used it. It can create a warm band,” she adds.

However, this process is very time-consuming and puts your hair at risk for more breakage, Paglionico notes. Translation: double duty isn’t a great idea for those with already brittle locks.