Will you ruin a perm if you straighten your hair?

Thermally styling hair with a flat iron or curling iron does not ruin a perm because perms permanently alter the shape of the hair and thermal styling only temporarily alters it. However, the repeated tension and heat involved with heat styling can cause damage, which can result in lifeless hair.

Hair that is thermally straightened with a flat iron or another heat device reverts back to its natural state when it's wet or shampooed. If the natural state of the hair is curly due to natural wave or the presence of a chemically induced permanent wave, the hair becomes curly once again.