Strange rash

My 4 year old son keeps breaking out in an itchy rash. It looks similar to poison ivy, with red patches, and raised bumps.  It started yesterday right below his eye, but within 30 minutes, it went away. Later on during the day, it broke out again, this time covering his face on one side, spreading to the back of his head, down his neck and in patches on his back and chest. Again, the rash went away within 30 minutes. When we woke up this morning, he had another break out on his chest, in a different spot.. it also went away quickly.  At first, I was thinking it might be an allergy, but he hasn't encountered anything new. Then I remembered, he was nipped by my mother's dog. The bite broke the skin, but it wasn't bad. Could the rash be related to the bite? Any suggestions on what might be causing the rash?

[Paige_Marshall]

I have a rash over top of a bite that I received a few weeks ago. My dog broke the skin only a little, but the bruising was substantial. I have an itchy rash above it now. I don't know what it is but I plan to ask my doctor when I see her.