We report a case of a 15-year-old atopic patient presenting with delayed, severe ulcerative hypertrophic gingivitis after placement of orthodontic braces, which required removal of braces and restorative laser surgical procedures. Patch testing to multiple metals and chemicals showed weak positive reactions to steel bands and formaldehyde. The patient experienced urticarial, gingivitis, and other intraoral symptoms after patch testing and re-exposure to nickel-containing products. In contrast, nickel, cobalt, and cobalt-chromium (Co-Cr) bracket patch testing sites were negative. Nickel-caused contact dermatitis is Type IV delayed hypersensitivity reaction occurring at least 24 h after exposure. This reaction can result in intraoral blisters, ulcerations, eczematous and urticarial reactions of the face and more distant skin areas. This case illustrates the intraoral delayed response, symptom resolution after removing the braces, and brackets and local reactions upon subsequent nickel exposure, despite negative patch testing and lymphocyte stimulation test to nickel. This case further illustrates the difficulty associated with diagnosing nickel allergy.