Why does dermatographic (or idiopathic chronic) urticaria tend to get worse at night / before & during sleep? when i wake up, it's much less severe.

Chronobiology: When one wakes up, the body is pumped with with epinephrine( norepinephrine) and steroid to prepare for hunting or gathering. These agents need to be mostly shut off at night to allow you to fall asleep . Since both of these agents counter itching and hives, they can account for what you have observed. There may be other factors involved but this is the simplest explanation.