Colorimetric Analysis of the Skin Reaction by Patch Test

Patch tests have been used to determine the existence of metal allergy, and its severity was ascertained by the change in skin color. However, it was quite difficult to accurately assess the change in skin color at times. Therefore, a new colorimetric diagnostic system capable of objectively evaluating color was developed to overcome this problem. This was made possible with the aid of a computer and spectrophotometer capable of making longitudinal colorimetric studies and analyses. When this new diagnostic approach was compared to the conventional subjective one, the following characteristics were obtained for positive testing ones: 1. Spectral reflectance curve was of the absorption type. 2. Depth of shade (Labe θ) increased. 3. A high color difference (dE) value was observed. 4. According to the Munsell system, the hue moved toward YR. 5. Lightness decreased and there was no change in chromaticity. 6. According to the CIELAB color system, there was a decrease in L*, an increase in a, and a decrease in b*. In conclusion, characteristics of this new objective approach showed significant differences in dE, spectral reflectance curve, Labe θ, and L*, a*, b*, and Lightness when comparing the negative and positive groups.