Milk hypersensitivity is a problem that can have substantial health, financial and social implications. The condition is underdiagnosed by some physicians and overdiagnosed by others probably because its symptoms are varied and shared with many other diseases. The gap in our knowledge on the pathogenesis of various manifestations of CMA has been only partly bridged by the information accumulated in recent years. It has become clear that milk-sensitive patients are heterogeneous, both regarding symptomatology and underlying pathogenic mechanisms.