New tricks for an old assay.

For decades, a number of guinea pig tests have been used to identify human contact allergens in workplace and consumer products, but these tests have limitations. In addition to using large numbers of test animals, they also provide only subjective measurements, because the allergic activity is measured by watching the skin for redness. Furthermore, coloring in some chemicals that are evaluated may mask reddening of the skin, thus obscuring the results. Since the 1980s, investigators have sought alternative test methods that would reduce the number of animals required and address the limitations of current tests.