Heat rash?
Google heat rash, and look at the "images" of heat rash, and see if your daughter's looks similar. There are different types of heat rash too.
My son had a rash recently, and it was heat rash.
http://www.medicinenet.com/heat_rash_pictures_slideshow/a...
Does the rash cause her pain or itching or anything?
There is also a cream called "Florasone Cardiospermum" cream, which is for skin conditions/eczema/rashes etc. and is all natural. You can find it at places like Whole Foods and natural food places.
Also, does she eat any citrus? Oranges or orange juice for example, causes a rash/eczema in my Mom. So does anything with Oatmeal in it.
Since it is all on her LEFT side.... is that the side she sleeps on?????
Via your daily observations of her and her activities, what is she doing, mostly that is with her left, side?