Both texturizers and relaxers are chemical treatments that break down the bonds of each strand of hair, causing subtle damage, making it unwise to use them too close together. It is for this reason that the instructions on both chemicals say to apply them only to new growth.
Relaxers and texturizers are typically used by African-American women to make their hair more manageable. While relaxers are used to straighten the hair completely, texturizers soften the curls gently, creating manageable hair without losing all the curl. The two products contain the same active ingredients, the difference being the application and time left on the hair. Using both of these products, even with a break in between may cause damage similar to applying a perm over relaxed hair.