White Gold began gaining popularity in the early 1900’s as an alternative to platinum. Platinum was steadily becoming more fashionable, but because of its rarity many could not afford it. Then, during World War II the government put a ban on the use of Platinum for any non-military functions and the demand for White Gold skyrocketed.
The most common alloys added to gold to produce white gold are nickel, palladium and silver. Most white gold jewelry is also given an electroplated rhodium coating to intensify brightness.
Throughout this process, white gold retains many of the benefits of gold. It won’t tarnish and due to the metals added, it is stronger than its yellow counterpart.
Recently, palladium has replaced nickel as the common alloy in white gold. It seems that a small percent of the population-approximately 12-15%-has an allergic reaction to nickel causing skin irritation and rashes. It is now required by law that jewelry pieces containing nickel be labeled “nickel-containing.”
Sources:
http://en.wikipedia.org/wiki/White_gold
http://www.gold.org/jewellery/technology/colours/white.html
http://www.govmint.com/knowledgebase/PreciousMetals.aspx