Same for me.

My biopsy did show positive results for PN. However, Dupixent was not effective for me.

Interesting. Maybe why people (myself included soon) try Dupixent ®.

The itching comes from within. Oversensitive nervous system in combination with T cells overproduction.

Within - If it was outside, I think many of us would have scrubbed that right on off!!
It has many things said, but it is in blood, but is reactive with the neuro lines, and can be within bloodlines, as some have it in their family lines. It is not transmissible.
Most of us have at least one other factor, such as cancer, another skin condition, health condition, such as asthma, copd, Lupus, etc..