To me this screams contact dermatitis.  That would also explain the patchiness.  Does the mother use a spray deodorant that may drift to the breast and midriff?  Perfumed powder?  Drift from hairspray?  Nipple or breast creams which may be okay on the mother but not the baby?
Has the mother been swimming, with chlorine still on her skin?
It sometimes takes ingenuity to figure out a cause for contact dermatitis.  It may not be something that readily comes to mind.
Virginia

Dr Virginia Thorley, OAM, PhD, IBCLC, FILCA
Brisbane, Queensland

Adria Cannon wrote:
> 
> For about the last 24 hours, every time this baby nurses she (the  
> baby) breaks out in a rash on her face and upper torso. The rash  
> starts to show a couple minutes into the breastfeeding and lasts for  
> about an hour. The mother describes the rash as patchy with clearly  
> demarcated red areas with some raised places within the red areas. The  
> red patches are in different places at different feedings. The baby  
> doesn't seem bothered by the rash. The baby's pediatrician isn't  
> concerned but the mother is... She called me because the rash appears  
> when the baby nurses.
>

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