I chose to use Titanium posts on all of my wood studs because so many people have 'sensitive ears' and titanium is the most hypoallergenic element. Titanium is ideal and the preferred material because it does NOT contain nickel. It is not an alloy. It is an elemental metal.
I use Grade 1 titanium which is the first of four commercially pure titanium grades. It is the softest and most ductile of these grades. It possesses the greatest formability, excellent corrosion resistance and high impact toughness.
Titanium: No Nickel at all
Stainless Steel: Is a metal alloy. Surgical - grade stainless steel contains a small amount of nickel.
Sterling Silver 925: Is a metal alloy. Genuine sterling silver contains 92.5% silver, 7.5% copper, and possible other metals like zinc or nickel.