You’ve probably heard (and maybe even experienced) your fair share of at-home hair color horror stories. But DIY dye does have its perks. It saves you the time and hefty price tag that come along with a salon appointment—if used correctly. There are certain situations, though, when you absolutely shouldn’t try to change your hair hue on your own.
First things first: The good news is that all hair types and textures can use at-home color—the trick is finding the right one. If you’ve got thick or curly hair, George Papanikolas, Matrix celebrity colorist, recommends gel or liquid formulas because they’re easiest to distribute throughout your head.
Meanwhile, foam dye is best if you’ve got fine hair—or sensitive skin. “A foam won’t weight the hair down,” says Papanikolas. “And if you have sensitive skin, the foam won’t drip onto the face or hairline, which can cause minor or severe breakouts.”
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Hair that has previously been chemically treated with a perm, relaxer, or straightening treatment can be colored, says Papanikolas. “[However], I don’t recommend highlights, as getting both [color and highlights] can result in damage and uneven porosity,” he says. Double-processed hair is also more prone to breakage because it dries out easily, so use a hair mask once a week. We like Matrix Hydrasource Mask ($23, ulta.com), which also adds shine. Korres Almond and Linseed Mask ($21.50, sephora.com), which contains B vitamins to strengthen and prevent further breakage, is another good choice.
The key with at-home dyes is to go no more than two shades lighter or darker than your natural color. “Any lighter and it gets brassy,” says Papanikolas, “any darker and it looks harsh.”
When choosing your color, do so based on whether you’re cool or warm. (To find out which one you are, look at your veins: If they’re blue, you’re cool-toned, and if they’re green, your warm-toned.) Cool tones should opt for cool ash browns and cool blondes (look for the words cool and ash on the dye box to make your selection). Meanwhile, “for warm tones, dark, warm browns, chestnuts, rich golden brown and auburn, warm gold and red highlights, and golden-blonde look best,” says Papanikolas.
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Here are three situations in which you should never do your color on your own:
…If You Want Highlights
When it comes to highlights, Papanikolas says they’re best kept in the hands of professional stylists. “I don’t recommend doing [highlights or ombré] at home because they’re too complex,” he says. Hand-paint too-large sections of hair by yourself, and you could end up reliving those dreaded frosty ’90s highlights. (Not a good look, right?)
…If You Want a Bold Blonde Color
“Going blonde from a box is hair suicide,” says Papanikolas. “A brunette or redhead to blonde requires highlights and several sessions [of dyeing].”
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…If You’re Trying to Lighten Previously Colored Hair
“You can color hair darker over previously colored hair, but color will not lighten previously colored hair,” says Papanikolas. To lighten strands that have been colored before, your hair would first need to be stripped out with bleach or a similar lightener. We recommend leaving bleaching to the pros.