Not necessarily. Depends on the type of hair you have. I used bleach on my fine greasy hair for years when I was younger and it helped to keep the grease away. It never got out of condition. My blonde streaks now are pure bleach, done by the hairdresser and my hair is still in good condition. However, I would take some professional advice if you are worried. (I presume you are talking about proper bleach for hair!)