As long as you only use the new relaxer on the new growth you shouldn't have a problem. Also if you are going from lye to lye or no lye to no lye then it should be alright. However things get tricky if you want to go from lye to no lye or wanting to use the new relaxer on the previously relaxed hair in order to "correct" it. Others have done this succesfully but you need to find a stylist that knows what they are doing and that you can trust. Be careful out there