Hair that has been relaxed using a thioglycolate based product should not be subjected to additional strong chemical treatments due to the risk of severe hair damage or breakage.
Hair that was relaxed with a thioglycolate based product should not be treated with other strong chemical treatments, such as ammonia-based permanent hair color or bleach. The chemical reaction from thioglycolate involves breaking the disulfide bonds in keratin through the formation of dithiodiglycolic acid from thioglycolic acid and cystine. This process compromises the hair structure, making additional chemical treatments risky as they can further damage the hair or even cause it to break.
Chemical depilatories, for example, contain around 5-6% calcium thioglycolate in cream form to prevent runoff and maintain a high pH to break down the hair for removal. Although depilation does not destroy the dermal papilla and allows hair to grow back, combining such products with previously chemically treated hair could lead to excessive damage and is not recommended. After depilation, careful rinsing and conditioning are crucial to normalize the skin's pH.