Having blond hair comes with a lot of responsibility. Usually if you're switching to blond from any darker colour, you'll have to upgrade your hair-care routine to include a purple shampoo to keep your hair looking fresh and free of those brassy or yellow tones. These often occur as a result of the hair being exposed to UV rays and pollution, so the shampoo is used as a toner to get rid of them. Purple shampoos are most often associated with hair that's been bleached blond, and you can use them on naturally blond hair as well, though it's not always necessary.
"Purple shampoo can technically make naturally blond hair less brassy," Devin Toth, hairstylist at New York City's Salon SCK, told POPSUGAR. "There are two specific things to keep in mind. First, most naturally blond hair isn't brassy. Second, purple shampoo works best in hair with an open cuticle, meaning on extraporous hair, and naturally blond hair isn't as porous as chemically processed blond hair."
There's a little more to know about that last part. The cuticles on your hair can open up from being coloured, chemically processed, or heat styled too often, not to mention brassy undertones can also be caused by harsh chemicals in the water you use. If you have naturally blond hair that's often being put through any of the aforementioned processes, it may be in your best interest to use a purple shampoo, but Toth noted that you shouldn't use it too often since "it can dry out your hair, make grey hair purple, and dull your shine" if overused. Purple shampoos should typically only be used once or twice a week.
Toth also recommends getting a gloss at a salon to enhance your naturally blond hair, then following it with a purple depositing shampoo to help extend the gloss. Head over here to shop a few of our most trusted purple shampoo recommendations.