The psychiatrist I consulted after 3 dermatologists told me I was crazy explained why (and it's not because little bugs are coming out at night). Although scabies will be more active at night, most rashes will also itch more during the evening hours.
Here's why: When we wake up in the morning our body's natural steroid levels are at their highest and they decrease as the day progresses. This is why fevers are higher at night, flu symptoms are worse, DH ITCHES MORE, etc. etc.
Why does a psych know this when regular docs don't?