Forget what you have been told. Hair toning is much more important and complex than simply putting purple shampoo on your hair. (opens in new tab) Here's the thing: When you dye your hair (opens in new tab) or highlight it, the color oxidizes and changes over time. For example, on platinum blondes, highlighted areas tend to take on a shiny yellow tint, rather than the cool tone they had when they came out of the salon. Brunettes and redheads, on the other hand, may find that their dyed highlights turn ashy as they try to add warmth and dimension to their hair color.

"People with colored hair should use a toner. All hair color fades over time with washing and heat styling," explains Shvonne Perkins, Master Stylist at Madison Reed (open in new tab). 'Imagine losing just a little bit of color every time you shampoo. So, just like your bank account, you have to keep depositing so that it gets withdrawn"

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Keep reading for a crash course in what you need to know about in-salon and at-home hair toner options.

Hair toner is a semi-permanent dye that will return your hair to your desired tone. "Toners deposit specific pigments into the hair that either counteract the tones you don't want to see (think using purple tinted shampoo to counteract yellow tones) or accentuate the tones you do want to see (like adding golden champagne tones to blonde hair for complexity)," Perkins explains.

Toners are often used with glosses and glazes. Gloss, glaze, and toner all essentially do the same thing," explains Kathy Cohen, colorist at Sharon Dorham in Sally Hershberger, New York. 'You can intensify or weaken the tones while adding sparkle.'

If you've ever had your hair highlighted or colored, chances are your stylist has sealed the deal with toner. Toner is the final step in the coloring process that weakens unwanted tones to make your hair neutral and sandy." Often this is done in the shampoo bowl, a process that takes about 20 minutes and you never actively look at," Perkins explains. A good formulation (which your stylist will mix for your hair color) will help bring out a specific shade. 'Maybe you want more copper, more violet, more gold, etc.'

While a salon appointment is your best bet for a true touch-up, there are also commercial toning shampoos and drops that promise similar color correction. "They extend the life of the color, slow fading, plus add more pigment so the hair stays vibrant and dimensional," says Perkins. Says Perkins, "If you have color-treated hair, a tone-up shampoo should be part of your rotation. It is a one-stop store for cleansing and toning."

However, home toners are not for everyone, and it is important to choose a solid formula. Cohen explains that many drugstore toners can be excessively drying if used incorrectly. If the wrong formula is used too often, hair will look dry and dry rather than shiny.

Toners cannot and should not replace the process of lightening bleached hair. Glosses and toners cannot actually lighten hair, even if you notice the hair fading. Properly toned color does not necessarily lighten the shade, but may appear brighter because of the cool tone.

Toners are semi-permanent, so it is best to tone your hair between and during the dying process. Olivia Casanova, colorist at IGK Salon in New York City, explains, "This is the best quick fix."

How often you should tone your hair between washes depends on your hair color. Courtney Lee, colorist at Kinloch Salon in New York City, explains, "Redheads tend to fade the fastest and generally need to touch up their color more often."

As for toning shampoo, use purple or blue shampoo every 3 washes. Follow the instructions and do not leave it on for "extra time" to get more pigment. If you need [color correction], increase the frequency of use, not the leaving time," Perkins adds.