Most temporary dyes work by simply coating the hair.
They tend to be hypoallergenic and do not cause harm to your hair. However, since they are removed by simply washing ones hair, they tend to bleed and require frequent re-dyeing. We do recommend using temporary dyes as a trial run before permanently going to a wicked color. Parents are more hip on the idea of the color washing out quickly. Lots of people find out that they weren't down with having wicked colors in the first place.