Lanthionization primarily occurs during which type of chemical service?

Lanthionization is a specific chemical process that occurs primarily with hydroxide relaxers. During this process, the disulfide bonds in the hair are broken and reformed, which leads to a straightening effect. Hydroxide relaxers, which use a strong alkali (such as sodium hydroxide), facilitate this lanthionization effectively, resulting in permanent changes to the hair's structure.

In contrast, other chemical services like acid wave perms focus on reforming hair through a different mechanism involving the use of thioglycolic acid, while color retouching and bleaching services are primarily aimed at altering hair color rather than changing its structural properties. Thus, lanthionization is specifically associated with the use of hydroxide relaxers, making it the correct association in this case.