Quoting Elsie Grim:" Soo, my daughter has a rash starting behind her ear, down her neck, on her chest and a bit on her side. ... [snip!] ... pardum check in and I didn't notice it then or I would have asked the midwive about it.. anyone ever had anything like this?"
Look up pictures of Eczema on babies/toddlers and see if it looks like that. Give her some benadrill just in case it's an allergic reaction. My son started getting bumps on parts of his body around 2mo, they were red, and if they got bad enough he would rub up against everything scratching them and they would start oozing a clear liquid and start bleeding if you don't take care of it or if it gets bad enough. If my son sweats and if he gets in the sunlight he has a breakout. But his carseat was triggering it on the back of his legs, beck, head, back, etc. It could probably be a number of things, so I would take pictures of it to show the doctor while it's flaring up, and get good close up pictures as well in case it clears up before you get her in. I will admit that unless I know my son has been in the sun *like going from the truck, into wal-mart. I tend to mix up his eczema with allergic reactions. I usually bathe him, cover him in his special cream the doctor prescribed and give him benadrill just to cover the basics.