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While some people are lucky enough to dye their hair and be thrilled with the results, many of us have the opposite reaction, or at the very least want to make some changes to the color. But dyeing over previously dyed hair gets tricky, because after all, dyeing hair is a chemical process and any chemical process does some serious damage to hair. That means coloring over dyed hair is going to require some careful choices and a little pampering.
Wait as long as you can before you color over the previous dye job. This gives your hair a chance to recover and rebuild from the first chemical process. Experts say you should wait at least one week after doing a solid color process and between two and eight weeks for the best results.
Deep condition your hair as much as you can before you re-color it. Coloring your hair is really drying, and dry, brittle hair not only breaks easily but may not take the new color as well. Use a deep conditioner two or three times a week and leave it in your hair for 30 minutes or more. For added conditioning power, put a shower cap on after putting in the conditioner and wrap a warm towel around it.
Choose a demi-permanent or henna color for dyeing over colored hair. Demi-permanent color lasts shorter than permanent color but is less harsh, which will help protect your hair. Henna hair dye is made from natural ingredients and is also less damaging than typical color. You can buy henna or demi-permanent color kits at most beauty supply stores.
Be sure to color over all of the previous hair color for the best results and to prevent it from looking streaky or uneven. You might want to have a friend help to make sure you color over even hard-to-reach areas. Leave the color in for 15 to 20 minutes or as instructed on the hair color kit.
Wait at least 24 to 48 hours after re-coloring to wash your hair. When you do wash your hair, pick sulfate-free shampoo and deep conditioners meant for colored or processed hair.