There are many different methods for testing the mildness of personal care products, and numerous factors that can affect the data collected. As a result, the definition of mildness will differ between laboratories. Therefore, one could argue that mildness is in the eye of the beholder. Recent work at the author’s company, shown here as a case study, has involved the development of mild body washes for sensitive skin, and examples of the tests used to describe the mildness of the products developed are given. Also, to understand skin’s responses to such tests, e.g., irritation and sensitization (see Figure 1), an overview of the mechanisms involved and skin conditions affected by cosmetic products are described, including skin barrier function and variations in skin sensitivity linked to skin disease, body site, ethnicity and age.