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A procedure, using Freund's complete adjuvant test (FCAT), for the determination of the allergenic potential of fractions and components in colophony of the gum rosin type is described and discussed. Gum rosin was shown to be a potent sensitizer in 11 test series (153 animals). FCAT is compared with the guinea pig maximization test (GPMT). Gum rosin was a potent sensitizer according to this method as well. The FCAT method was found to be advantageous over the GPMT method in that it is technically simpler to use and a smaller amount of test substance is needed. However, closed challenge was preferred to the prescribed open challenge. The importance of statistical evaluation of the results obtained in predictive testing is stressed.

Disappearance measurements have been used for studying the inhibiting effect of barrier creams on chromate (⁵¹Cr) absorption in the guinea pig. The creams Bakosan, Dow (Silicones), Indulona, Ivosin, Kerodex 71 and petrolatum were applied in different volumes (0.05–0.15 ml/cm²) and the interval between application of cream and chromate was varied. Ivosin (ion exchanger) was the most effective absorption-inhibiting preparation. Only at 0.15 ml/cm² was Dow equally effective. The protective effect of Bakosan, Indulona, Kercdex and petrolatum diminished when the volume was raised to 0.15 ml/cm³. Increasing the interval resulted in no change (Ivosin), a decrease (Bakosan, Indulona), and an increase in absorption for the other creams. Film thickness and interval before exposure have clinical implications.

The percutaneous absorption rate of trivalent (CrCl₃) and hexavalent (Na₂CrO₄) chromium through excised human and guinea pig whole skin was determined by an isotope method (disappearance measurements). No difference in absorption between the compounds was observed. Thus, the lower absorption of CrCl₃, obtained with the same method in vivo, could not be verified. The ratios between the in vivo/in vitro rates for CrCl₃ were lower than 1; for Na₂CrO₄ they were concentration-dependent. The pH changes in chromium solutions after contact with guinea pig skin were greater in vitro than in vivo. Extrapolation of the results to in vivo conditions in man is not considered possible.