What Is The Large Bright Red Spot On My Back?

Hi, I noticed today that I have a large bright red spot on my back. My boyfriend mentioned it to me a few days ago and I thought nothing of it, as I recently got several mosquito bites on my back (which I am highly allergic to). I figured he was referring to one of this swollen spots. However, this spot looks very similar to a bruise only it is red and has not turned purple or yellow at all. It is not painful, but it has been itchy in the past couple of days. It looks as though blood has leaked under my skin and it is about the size of a silver dollar, maybe a bit larger. What the heck is this? Will it go away? Like I said, it is not painful, but it is hideous!