During a chemical relaxing procedure or a hydroxide relaxer, a process called lanthionization occurs, which is the breaking of a disulfide bonds in order to alter the natural curl pattern of the hair. During this process the curl pattern is loosened or relaxed. The cortex is thus elongated, stretching the original curl pattern, therefore making this a permanent alteration.
Often times Guanidine hydroxide relaxers are recommended for clients who have a sensitive scalp. These forms of relaxers such as Design Essentials Sensitive Scalp relaxer tend to be less irritating to sensitive clients.