Evaluating lotion transfer from products to skin using the behind‐the‐knee test

Background/purpose: Adding lotions or emollients to the surface of a variety of paper products confers a number of benefits to the skin of consumers. A modification of the ‘behind‐the‐knee (BTK)’ test model was used as a means of measuring the effectiveness of lotion transfer to the skin. Methods: Two series of feminine protection pads were prepared: (1) identically constructed pads differing only in the amount of lotion applied to the surface and (2) pads of various compositions to compare the influence of other product characteristics. For the first series, pads were applied for 3 h using the BTK protocol, and lotion transfer was evaluated. For the second series of products, two sample pads were applied consecutively for 3 h each, and lotion transfer was evaluated a both time points (e.g., 3 and 6 h). In addition, a clinical in‐use study was used to evaluate lotion transfer for the second product series. Results: In the BTK model using pads of identical composition, lotion transfer was a function of the amount of lotion placed on the pad. However, results from the second product series indicated that when pads were prepared using different absorbant materials (supreabsorbent gelling material, or AGM and cellulose), pads with the AGM core transferred lotion more effectively than pads with a cellulose core. Other product characteristics, i.e., pad thickness and lotion configuration, did not detectibly influence lotion transfer. The results of an in‐use clinical study conducted on the second series of test products were directionally similar to those from the BTK, but statistical significance was not reached. Conclusions: An adaptation of the BTK test method provides an effective means of evaluating the transfer of lotion formulations from feminine protection pads at a fraction of the cost of clinical in‐use studies.