It is not possible to reverse a hair relaxer, which is a permanent hair product. The only way to get rid of the result of a hair relaxer is to grow out the hair. Cutting off the processed hair allows the new growth to come in with a natural look.
Some people have claimed that relaxers can be removed from hair by washing the hair with dish detergent or vinegar, or by soaking it with a combination of mayonnaise and eggs. Unfortunately, none of these claims is true. Washing the hair with detergent only produces dried-out, unhealthy hair. Hair grows at about 1/2 inch per month, so returning to a natural look takes several months.