Methods, formulations, and kits for curling and/or preventing damage in the curling of hair are disclosed herein. Hair can be curled by treatment with hydroxide-containing agents, in combination with one or more active agents, without the need for thiol-based or peroxide-based agents. The active agent can be applied simultaneously with the hydroxide-containing agent, to impart curl to the hair. They may be applied as a combined formulation or as separate formulations applied simultaneously. Use of the active agent along with a hydroxide-containing agent can be used to control the level of curl imparted to hair, as compared to the natural amount of curl, if any, in the untreated hair.