Cosmetologists recommend waiting around 4 weeks before re-coloring hair. Dry, damaged hair should only be colored every 6 to 8 weeks.
Many people color their hair often if they don't achieve their desired color the first time around or because they simply want to change their look frequently. However, coloring hair can cause substantial damage to the hair shaft and may cause split ends and breakages. Hair should be deep-conditioned between coloring to improve its strength.
It is usually less damaging to color hair a darker shade than to go lighter. Those who prefer changing their color frequently often use semi-permanent hair color, which inflicts less damage on the hair than permanent colors. People who want a more permanent color can reduce damage by going with a 10 or 20 developer and leaving the color on for less time than is typically recommended.
People lucky enough to have strong, healthy hair can get away with coloring every four weeks or so. No matter how often a person colors his or her hair, using a deep conditioner every week can help to restore hair and prepare it for the next color application. If the hair looks dull, breaks off easily or shows signs of split ends, it is time to take a break from coloring and to get the hair back in good condition.