What Causes Itching On Scalp, Lower Abdomen, Back And Torso?

I am 36 yr old female w/ what started as scalp itching ( I thought from getting hair colored) approximately a weekand a half ago. Last night the itching started at lower abdomen and became progressively worse today. Noticed petichiae on back & torso today at work, but don't know if petichiae related to itching or not. Any thoughts?