Toddler's skin rash

My 3yr old has a rash that started about 2 months ago on his leg, near his knee.  It started off small and I thought it was a little scrape.  It got a little bigger and goes from being beige and rough looking to red and rough looking.  In the last week or so he now has another on his forehead and in the last couple of days has about 3-4 more on his hairline and one or two on his back.  Those are all beige, fairly flat, but roughish.,  Yesterday he had another 10 bumps or rashes show up but these almost look more like bites as they are red.  Mostly on his back but a few on his arms.  He's not itching so although a pediatrician saw him with the very first rash and said it was probably just eczema I'm starting to wonder. It has been pretty hot here, but it doesn't look like heat rashes I've seen before.
any thoughts?