Our a\c went off in the night and yesterday it took forever to get the repair man out so we had our newborn in the heat all day long with nothing but fans...did the best we could, but she has terrible heat rash...what can I put on it to make it better???
. . . and I, personally, would not use the cornstarch.
In heat & humidity it would provide an excellent medium for bacteria.
Instead bathe the prickly heat rash with a highly dilute solution of water & baking soda.
My daughter (a July baby) got this when she was tiny, too.
I would steer clear of aveeno on a baby.
Perhaps get some bulk organic oats and put them in the bath water.
You can put them in some thin cloth or a tea bag.
we had no ac in tucson until my son was 1 month old.
I used to rub him with cool rags all day.