Gold filled is not to be confused with gold plating as filled literally has 100% more gold than gold plating. Gold filled jewelry is much more valuable and tarnish resistant. It does not flake off, rub off or turn colors.
As a matter of fact, anyone who can wear gold can wear gold filled without worries of any allergic reaction to the jewelry. Gold filled jewelry is an economical alternative to solid gold!
Gold plated jewelry source: