Hypersensitivity reactions to orthopedic implants are a rare cause of implant failure. Epidemiological data regarding this issue is insufficient. Orthopedic implants containing nickel, cobalt, and chromium are the most frequent cause of hypersensitivity reactions. The pathophysiological mechanism of this condition is a type IV hypersensitivity reaction, also known as the delayed hypersensitivity reaction. The most dominant symptoms are non-specific ones like pain, swelling, and limited range of movement at the implant site. Localized or systemic skin changes, as well as delayed bone and wound healing, can also occur, together with some less frequent symptoms. During the diagnostic process, infection and mechanical irregularities must be excluded first. The patch test is the golden standard for diagnosing hypersensitivity reactions to orthopedic implants. In vitro tests can also be used, and the lymphocyte transformation test is the most common one. The most effective therapy is revision surgery where the allergenic implant is removed and a hypoallergenic one is implanted instead. As a preventive measure, the patient's history of metal hypersensitivity is obtained. If the patient reports previous metal hypersensitivity, a preoperative patch test is done. If the test turns out to be positive, a hypoallergenic implant is used in the following surgery. Additional scientific studies have to be done in order to create evidence-based diagnostic and therapeutic guidelines.