So-called metal allergy is a new interesting subject in orthopedics. Two different ways of thinking prevail in the literature. In the German orthopaedic literature, the diagnosis of metal allergy is often described and considered a real pathology, while we can find a more skeptical approach to this entity in Anglo-Saxons literature. Being an exclusion diagnostic, without any universal consensus on how to diagnose or on the treatment, the aim of this article is to clarify what we know about metal allergy today.