A computer program for the analysis of differences or changes in skin sensitivity has been developed. It is based on parallel line assay, and its main features are its ability to conduct a validation process which ensures that the data from skin tests conform to the conditions imposed by the analysis which is carried out (regression, parallelism, etc.), the estimation of the difference or change in skin sensitivity, and the determination of the 95% and 99% confidence intervals of this estimation. This program is capable of managing data from independent groups, as well as paired data, and it may be applied to the comparison of allergen extracts, with the aim of determining their biologic activity, as well as to the analysis of changes in skin sensitivity appearing as a consequence of treatment such as immunotherapy.