Hydrolyzed formulae are created by using enzymatic processes to break native proteins into smaller fragments. They may prevent development of allergic diseases by reducing exposure to intact allergens. Partially hydrolyzed whey formula (pHWF) is particularly promising for allergy prevention, as it is cheap to manufacture and palatable. Scientific organizations have recommended the use of hydrolyzed formula in the first 4-6 months of life for the prevention of allergic disease based on a limited number of trials. Three recent developments challenge these recommendations: our growing understanding of the importance of allergen exposure for induction of immune tolerance, recently published evidence that failed to identify a protective effect of pHWF, which the authors and other experts believe will necessitate updating of systematic reviews, and methodological limitations of available trials and systematic reviews on which these recommendations are based. Until more definitive evidence is obtained, the authors recommend continuing to advocate that 'breast is best', and caution against overstating the potential for pHWF to prevent allergic disease.