Fluhr eta/. (10) and Clarys eta/. (11 ) both reported significant correlations between the
different instrumental readings. Figure 2 shows plots of our data from each instrument
against each of the others. Our data are in agreementhat there are significant correlations
between the different instruments. Correlation coefficients from these plots are
compared to literature values in Table IV. Our correlation coefficients are lower than
those found by Clarys et al. for Nova © vs Skicon © readings and Nova © vs Corneometer ©
readings, but compare well with those of Fluhr eta/. The correlations between Nova ©
and Skicon ©readings were the highest, afinding that is also in agreement with Fluhr eta/.
CONCLUSIONS
At all NaC1 levels and with each instrument, readings were linearly correlated with
glycerin concentration. Since glycerin is both a humectant and an effective skin moisturizer,
we assume that this increase in the instrument readings is caused by an increase
in skin water content. However, we cannot rule out the possibility that the increase in
the readings is directly caused by glycerin through increases in polarizability of the
media.
The presence of sodium chloride decreased the readings slightly in the absence of
glycerin and increased the readings in the presence of glycerin. The maximum effect was
at 1.5% salt and 5% glycerin. The salt-induced increase in the presence of glycerin was
statistically significant with all three instruments at 1.5% salt but was less at 3.0% salt.
We anticipate that the explanation of the effects of salt observed in this study is related
to the levels of moisture attributable to the formulations. Specifically, at low levels of
hydration, i.e., 0% glycerin, there may be insufficient water remaining in the stratum
corneum to fully ionize the NaCI, thereby diminishing the conductivity relative to
formulations containing glycerin. The hygroscopicity of glycerin may provide water for
solubilization of the NaC1. Our results indicate that salt by itself will not cause large
positive artifacts in electrical readings.
REFERENCES
(1) M. Loden, Biophysical methods of providing objective documentation of the effec