While readily accessible, the skin presents many problems in measurement including its flexibility and its reactions to many procedures that might be used. A list of many possible measurements is given and specific measuring solved in the course of our work presented. The relationship of visual grading to measurement is discussed. Different examples of description and measurement in dermatological work are discussed in terms of the nominal, ordinal, equal interval, and ratio scales studied by S. S. Stevens.
Daniels F, van der Leun JC. Problems in Quantifying Skin Reactions. Arch Dermatol. 1968;97(5):553-565. doi:10.1001/archderm.1968.01610110061011