Assessment of cosmetic acceptance under normal conditions of use is one of the most important testing methods besides biophysical measurements. Here the products to be tested are applied regularly over a certain time period at home (home in-use phase) by several persons. Usually the studies are performed in volunteers with healthy and unproblematic skin. To familiarize the volunteers with handling the products, the first application is done under supervision in the institute before the home in-use phase begins. At defined time intervals the cosmetic acceptance and efficacy are assessed subjectively by the users themselves using a questionnaire in an interview situation (self-assessment, auto-evaluation).

Depending on the requirements on the test products test panel can be generated with defined skin problems and special criteria and/or monitored by medical specialists, usually dermatologists or ophthalmologists.

Often in-use studies are accompanied by biophysical measurements of the skin.