Dyeing hair twice in a row will be damaging to the hair. It is best to wait at least four weeks before dyeing the hair again.
When hair is dyed, the hair is weakened by the chemicals. Constant exposure to the chemicals will weaken the hair even further. Each time hair is dyed, the outer layer is stripped, and the hair shaft is damaged. The lighter the hair is dyed, the harsher the chemicals are on the hair. As a result, the hair needs to be treated with caution to prevent any further damage. Even if the color did not take properly, it is still best to wait between four to eight weeks before dyeing the hair again.