Dermatologist Dr. Howard I. Maibach of the University of California, San Francisco, and Dr. Jacob Pontoppidan Thyssen purchased 277 inexpensive earrings -- under $50 -- from 34 different stores and artists in San Francisco.

All earrings purchased were examined with the dimethylglyoxime, or DMG test -- a routine spot test to detect the presence of nickel.

Of the 277 earrings, 30.7 percent demonstrated at least one spot that tested DMG-positive for nickel. Price could not predict exposure. In one store, none of the 44 earrings costing $5 and $8 were DMG positive, but numerous earrings costing $15 o $25 in another store were DMG positive.

Maibach said that the highest proportion of DMG-positive earrings came from local artists, with 69 percent of these earrings testing positive for nickel. Forty-three percent of earrings purchased from stores in China Town also tested positive.

The study, published in Journal of the American Academy of Dermatology, found 24 percent of the earrings purchased at the stores targeting younger women tested positive for nickel, but only 1.7 percent of earrings from stores targeting women over 40 tested positive.