Allergic reactions raise the utmost concern to health care practitioners in all fields of expertise. Nickel allergy can be seen occasionally in orthodontic patients as nickel is a component of the majority of orthodontic alloys. The objective of this review was to discuss the prevalence of nickel hypersensitivity reactions, compare the nickel ion release during orthodontics treatment and possible alternative treatment options available for patients with a nickel allergy. Further prospective researches with large sample sizes are required to improve the quality of evidence.