My 23 month old toddler has a rash on his left side of his body. He has had it for about 6 days. It has been skin color that only started to turn pink today--probably because it is 80 degrees today. I am concerned about what is causing this rash and why it is only on his left. It starts under his armpit and travels all the way down to his left foot. Other than one of his two year molars popping through and a fever of 100--everything seems as usual. He is eating, drinking, pooping, peeing and sleeping fine. We've even started potty training in which he seems eager to learn. He is singing his alphabet, saying more and more words each day. So other than this concerning rash it seems he's on track developmentally.