Q: I recently dyed my hair black/dark brown and was told I can't dye over it again. I have to wait until it grows out. Is this true when I
only want to dye it the same color or a shade darker again?
A: If you've used a standard haircolor brand (purchased from a beauty supply and mixed with developer) and you want to use the same type of
product on your hair, then you should be fine to do so. You do have to be careful with certain types of haircolor (henna-based and metallic salt
haircolors for example) as these can react badly with regular haircolor mixes.
However, if all we're talking about is a change in color using standard beauty supply colors (not the
haircolor kits from your supermarket or pharmacy) you should be able to safely recolor your hair. You could even lighten the haircolor if you
want in this situation, although lightening previously colored hair should be done with caution to avoid unpleasant results. You should also
avoid lightening the hair too much from the color you have now or you risk damaging the hair because it has already been color treated and will be more responsive to lightening.
Now if you were told by a salon professional that you have to let the haircolor "grow out" you need to
understand the reason you were told this. However, I'm guessing that you weren't told this by a salon professional because he or she should have
explained the reason you "can't dye over it again".
Anyway, if you only used standard haircolor, and your hair is undamaged from the previous color
process, then you can feel free to recolor your hair. Just be sure to use the same base color in the new color as you did in the original color
to avoid any unwanted color conflict problems.