I have some dead skin on my scalp 4 months after FUE. Will this affect my results?

It is best to ask your surgeon about post operative care as each doctor has their unique regimen.  Dead skin will not affect your results.

A photograph of the area would be helpful. Generally speaking at 4 months post-op there is little that can happen that would damage the grafts.

Without a visual of your scalp, it is difficult to say; however, at 4 months post-op it is likely that the "dead skin" you see is problematic to your transplant. How often do you shampoo? At least twice a week is healthy for your scalp.