Final answer:
Never apply products with lithium hydroxide, sodium hydroxide, or other strong alkalis to hair previously relaxed with thioglycolate to avoid severe hair damage.
Step-by-step explanation:
Products containing lithium hydroxide, sodium hydroxide, or other strong alkalis should never be applied to hair that has been previously relaxed with a thioglycolate relaxer. These strong alkalis can cause adverse reactions when mixed with thioglycolate, leading to severe hair damage, including hair breakage and loss. This is because the hair has already been chemically altered, and the additional harsh chemical can overwhelm the hair's already weakened structure.
A permanent wave, commonly called a perm or permanent (sometimes called a "curly perm" to distinguish it from a "straight perm"), is a hairstyle consisting of waves or curls set into the hair. The curls may last a number of months, hence the name.
Perms may be applied using thermal or chemical means. In the latter method, chemicals are applied to the hair, which is then wrapped around forms to produce waves and curls. The same process is used for chemical straightening or relaxing, with the hair being flattened instead of curled during the chemical reaction