As defined by the Mayo Clinic, “Contact dermatitis is a red, itchy rash caused by a substance that comes into contact with your skin. The rash isn’t contagious or life-threatening, but it can be very uncomfortable.”
People with sensitivities to metal often experience this irritation on their earlobes when they wear any form of metal earrings. Nickel is one of the primary causes of contact dermatitis. The North American Contact Dermatitis Group reported that nickel sensitization rates increased from 15.5% in 2009-2010 to 18.5% in 2011-2012.  These rates continue to rise as the years progress. One study indicated that young women (under the age of 19) who had a patch-test used to test for metal allergies, experienced nickel sensitivities at the rate of 19-37%, and that women over the age of 18 experienced nickel sensitivities in the range of 18-24%.  Often, people who are allergic to nickel will also exhibit sensitivities to other metals used to make “hypoallergenic” earrings – including gold, titanium, silver, platinum, niobium and several others.
In the European Union, a law was passed in 1994 called the Nickel Directive to try to deal with the increasing sensitization to nickel.  This directive limited the amount of nickel that could be used in jewelry. Over time, it has transitioned into specifically limiting the amount of nickel that could be released from jewelry that contacted the skin. This directive has been absorbed into the European Union’s REACH regulations which continue to protect consumers from over-exposure to Nickel and other metals that may cause sensitization. Studies have shown that these regulations and accompanying changes in jewelry have been very helpful in decreasing the rates of nickel sensitivities.  The United States has not yet adopted such a law, but the need for caution when choosing jewelry is obvious.
 Warshaw, E.M., Maibach, H.I., Taylor, J.S., et al. North American contact dermatitis group patch test results: 2011-2012. Dermatitis. 2015; 26: 49-59