Whether there are side effects of semi-permanent hairline reflection

An acquaintance of mine has M-shaped hair loss and received semi-permanent treatment last year.

At first, it was okay, but as time went on, the treated area started to feel slightly red.
They say it's changing. I wonder if this phenomenon occurs naturally...
Or should I go to that hospital and speak more assertively about possible side effects?

At the hospital, my skin is simply sensitive and turns red depending on my mood.
It is said that it can change.

Although not very noticeable, properly treating the skin that has turned red.
Is there a way to turn it?

Thank you in advance for your response.