Cheap earrings that contain nickel are a common cause of earlobe dermatitis, say U.S. researchers who analyzed 277 inexpensive earrings (under $50) purchased from 34 different stores and artists in San Francisco. The study authors noted that repeated exposure to nickel can make it difficult to treat earlobe dermatitis.

The tests revealed that 30.7 percent of the earrings contained at least some nickel. The highest proportion of earrings with nickel came from local artists (69 percent) and from those purchased in China Town (43 percent), United Press International reported.

The researchers also found nickel in 24 percent of earrings bought at stores targeting young women, compared to 1.7 percent of earrings from stores targeting women over age 40.

Price wasn't a good indicator of whether earrings contained nickel. For example, none of the 44 earrings that cost $5 and $8 at one store had nickel, while many earrings that cost $15 and $25 at another store did contain nickel, UPI reported.

The study is published in the Journal of the American Academy of Dermatology.