Methods and kits for treating hair or preventing damage in the relaxing of hair are disclosed herein. Hair that is damaged during a relaxing treatment with hydroxide-containing relaxing agents, can be treated with formulations containing one or more active agents. The active agent formulations can be applied simultaneously with the hair relaxing formulation, or optionally applied immediately following application of the relaxing formulation, to reduce damage and breakage. Use of the active agent formulation along with a relaxing treatment can be used to control the level of curl achieved or retained in the relaxed hair, as compared to the natural amount of curl in the untreated hair.