As regards the rash, have you thought of non-food triggers, i.e. apart from viruses?  Here are some examples:
1)  Hairspray.  30+ years ago in the La Leche League News, a case was reported where the rash on the baby was linked to the mother's hairspray.  After she wore a cape or towel around her shoulders every time she sprayed, to prevent some of the spray contaminating her neck and clothes, the baby's rash cleared up.
2) Grass.  Is the baby, it the warmer weather, being put on the grass outdoors on a rug? If so, it is possible for there to be contact with the grass, either through wriggling to the edge of the rug, or from using the same rug and having the side which was previously against the grass uppermost.  At an older age, my eldest daughter used to get up, screaming, after rolling on the grass at my mother's place in play, and hives would quickly come up before my eyes.  (Putting her in a bath with a good handful of bi. carb soda relieved the hives beautifully.  Screaming stopped, and the hives went.)
    So, look at *contact* allergens, too, not only dietary ones.
           Virginia
           in Brisbane, QLD, Australia

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