The average person's hair grows about 1/2 inch a month. If you color your hair regularly, that's 1/2 inch of growth you don't want anyone to see. While dyeing your entire head of hair every month can damage your hair, touching up just your roots at home will save your strands -- and your bank account, if you got your dye job done at a salon. Focus on the roots around your hairline and part to cover up the growth that's most noticeable.
Choose a hair dye that will match your dyed color. When buying drugstore dye, pick a color in the tone you want but one shade lighter, as box color tends to dye slightly darker than indicated. You can also choose a root touch-up kit in your shade.
Part your hair the way you wear it most often, using the end of a rat-tail comb. Your hair should be wet if you're using a semi-permanent dye and dry and unwashed if you're using a permanent dye.
Rub a thick layer of petroleum jelly around your hairline at your forehead, temples and around your ears. If the roots around your neck show and you plan to dye them as well, apply petroleum jelly around your nape.
Mix the color according to the dye manufacturer's directions while wearing plastic, latex or rubber gloves. Drape an old towel around your shoulders to protect your clothing. Squeeze the dye into a plastic bowl if one is not provided – choose an old bowl or one that you will use only for dye jobs, as the color may stain.
Test the color on a small, inconspicuous piece of root hair behind your ear or on your neck. Apply it for the indicated length of time and rinse clean. If the color is a good match, you'll know it's safe to proceed.
Soak a cotton ball in the dye solution. Gently pat the dye on the roots at your hairline and into your part. If you’re using a root touch-up kit, use the applicator brush provided to apply the color to your roots.
Place the end of the rat-tail comb at your hairline about 1 inch to the side of your part, and carefully run the comb from your forehead to the back of your head. Lift this section of hair and lay it across your part -- a new line of roots should be visible. If you don't have a natural part, start in the center of your head and work your way out on either side.
Saturate the visible growth with your cotton ball or applicator brush, as far back on your head as you can reach. You may need assistance for this step, or you can check your progress with a handheld mirror. To see the back of your head, stand facing away from the mirror on the wall. Position your handheld mirror so that you can see the back of your head in your wall mirror. Use this method to touch up the roots behind your ears and at the nape of your neck.
Continue re-parting your hair, moving the new section of hair over to reveal more roots and dyeing the visible growth, until you have covered all of the new hair growth.
Allow the dye to set for the time indicated in the formula directions. Rinse the dye out carefully, starting where you applied color first -- your hairline and part. Rinse until the water runs clean. Wipe away the petroleum jelly with a washcloth or tissue.
Style your hair as usual and check your roots. Don’t throw your mixed hair color away until you’ve dried your hair; you may have to retouch roots that you missed.
48 hours before you apply any dye you haven't used before to your hair, test it on your skin. Mix a tiny amount of dye, and rub it on the inside of your wrist or elbow. If you don't notice any irritation, proceed.
Do not use the bowl that contained the dye for any other purpose.
If you're in a hurry or you don't want to retouch all of your roots, focus on just your hairline and your part. These are the areas others will notice, and touching them up will improve the look of your dye job overall.
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