Certain metals (especially nickel or gold) can cause contact dermatitis (see also “contact dermatitis”) A pre-operative patch test may help guide the selection of an implant in patients with high suspicion of metal allergy. Patients are typically asked to wear the patch for 48 hours, keeping it dry for that period. The allergist will then ask to return twice to check on the reaction. The patch test conducted by an allergist will determine what caused the reaction so that the allergen or irritant can be avoided in the future. The patient will receive a list of what they are allergic and also a list of products that they can use.