This is generally why professional body piercers are obliged to only use titanium jewellery which contains no nickel, under the EU Nickel Directive, or high quality implant grade surgical steel provided the wearer is happy that they do not have an allergy to nickel as it may still contain a minuscule amount of it.
Piercing guns can be credited to most of the reactions to jewellery because while the packaging on a gun stud may claim that the stud is titanium, it will only be titanium coated and that coating wears off, causing the nickel that the stud is made of to be exposed and cause a reaction. This also adds to the risk of infection in vagina piercings as the coating can flake off and become embedded in the piercing and trap bacteria.
There is also no guarantee with a ‘titanium’ gun stud that the butterfly back will be made of the same material.
Gun studs are generally poor quality. The only materials that should be used in fresh piercings are titanium, implant grade surgical steel, PTFE, bioplast, niobium or even glass jewellery is good.
For fresh piercings acrylic, gold and silver should definitely be avoided, alongside coated jewellery.
Hope that sheds some insight!
