What Could Be Causing An Itchy, Swollen Rash Mostly In The Evenings Around My Belt Line And Armpits, Sometimes With Lip Swelling?

Over the past month I have been getting an itchy swollen rash only in the evenings but not every night. It is typically gone by the morning when I awake. It is mostly around my belt line or arm pits but is not limited to those areas. I also woke up with my lips swollen this morning. The intensity level of the rash seems to have increased over time.