Hi Katherine,
It's so difficult when little ones get a rash or something that comes and goes. It can drive you crazy at times. Do you notice it more at some times versus others? Does she wake up with it or do you notice it more after she has been playing with something? The reason I ask is that she may be drooling while she's sleeping or rubbing her face on the bedding. Or if it is a toy, it could be the material the toys are made from. Just guesses. If you can try to see when it does appear, after some specific activity or after eating something in particular that might help. Do you clean with anything that she may be allergic to? There are so many products out there that use harmful toxins and chemicals in their products, especially cleaning products. A friend of mine was dusting and noticed that the spray was causing an allergic reaction with her son. That day onward she switched to products that don't contain harmful chemicals. I switched my products too and shop from an online store. Once I found out about all the harmful ingredients in products, that was enough for me.
I'd keep a watch on your daughter and see if you can make a connection to the time she develops the rash and what she was doing prior to the development. With all the recalls for toys, it may be a toy that she likes to suck on or something she likes to mouth. At 2 they are still putting a lot of things in their mouths. I hope this helps somewhat.
Best to you,
M.