You should not give a soft curl perm to a client whose hair is:

A soft curl perm, also known as a body wave, involves the use of chemical solutions to alter the structure of the hair, allowing it to hold a curl. However, it is critical to ensure that the hair being treated is healthy enough to withstand the chemical process involved in permanent waving.

When a client's hair has been relaxed with sodium hydroxide, it has already undergone a significant chemical process that alters its natural structure to make it straight. The use of additional chemicals, such as those applied during a soft curl perm, can lead to excessive damage, breakage, and potential scalp irritation, as the hair is already weakened from the relaxing process. This is why it is advised against performing a soft curl perm on hair that has been chemically relaxed with sodium hydroxide.

In contrast, hair that is colored with semi-permanent dye, natural and unprocessed hair, or thinning and fragile hair might all still be candidates for a soft curl perm but would require careful consideration and possibly a gentler approach. For example, colored hair often can tolerate some chemical processes, and natural hair may be ideal for curling. However, thinning and fragile hair would require caution and possibly specialized formulations to ensure minimal damage occurs during the perming process.