Why do silver earrings turn black?

Tarnishing is a biochemical reaction that slowly darkens and dulls silver earrings. Exposure to sulfur in the atmosphere and liquid forms a coating of tarnish on the surface of the metal, producing damage to lustre and shine. Silver oxidizes on a more accelerated pace in the areas with a lot of daylight and high moisture content. Further, contact with goods like cosmetics, spray, fragrance, deodorant, lotion, bleach, etc., can advance up the oxidizing process of the jewellery

Besides that, the oils that your outer skin gives out can react to your 92.5 Sterling Silver Earrings. The degree to which the silver responds with these items from your skin is very much dependent on the sort of food you consume, liquor intake, and whether you are using medications.
These things change the acidity of your surface, which can create a negative response. Also, perspiration increases the acidity and could blacken the silver.