The use of nickel in jewellery has been restricted, as this metal may cause contact allergy. The EU chemical regulation, REACH, restricts the allowable amount of soluble nickel in products. This regulation concerns products that will have long-term contact with the human skin and that may release nickel.
The amount of the released nickel by products can be analysed in a laboratory, and it must not exceed 0.5 µg/cm2 a week. In post assemblies that are used while the pierced body part is healing the amount of nickel that may be released is even smaller.