Rash attack

A couple of weeks ago we noticed a red spot on the back of Jake's neck.  We assumed it was just dry skin so we put lotion and A&D on it.  It looked like it was clearing up, so we weren't too concerned.  

But it never progressed past that.  Then we noticed patches of it on his legs.  Then we noticed angry bright red patches on his arm, that looked like fingerprints.

We talked about how we never grab him from there, only under his pits or his hands.  We didn't know why the one on his arm was shapped like that or why it was so angry.  Now it's spreading all over his back.  It doesn't hurt him, or bug him in any way.  We just don't like how it's spreading and how it looks worse at times.

I made a doctors appointment for tomorrow and hopefully we can get this cleared up.  I really hope it's nothing serious.