How 2 distinguish between baby acne, lactose intolerance, milk protein allergy, or soy allergy? I'm pumping + supplementing and don't know rash cause

Rashes common. I'm assuming your baby is fairly new Rashes need to be seen for correct identification Most of the food sensitivities have intestinal symptoms as well such as gas, irritability. rashes in very young infants are common and you should see your doctor for a proper visual ID.
Tough without seeing. Most babies aren't lactose intolerant. It's usually a milk or soy protein intolerance.If the rash is more of a dry eczema rash, it could be due to a protein intolerance. If your plan is to continue breast feeding, it is worth a try to take all milk and soy products from your diet. Neonatal acne is a pretty easy diagnosis. His MD can tell you what the rash is.