The most likely cause of your baby's loose stools is that she has developed an allergy to her soya formula.If her sister has eczema it is likely that she [her sister] is allergic to cow's milk rather than being lactose intolerant.So there is probably a family history of allergies. About one third of babies from allergic families who are fed on soya formulas become allergic to soya.Try her on a low allergy cow's milk formula such as NAN HA first. If she still has loose stools she will need to go onto an extensively modified formula such as Similac Advance Alimentum.
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