When Good Science Leads to Bad Assumptions: Misconceptions in Cosmetic Product Development

Good science does not automatically translate into a good cosmetic product. In this Perspective, we examine four recurring misconceptions: that ingredient evidence can stand in for finished-product performance; that more actives, higher concentrations or greater complexity necessarily improve outcomes; that a product that remains safe and physically acceptable is therefore functionally unchanged; and that microbiome compatibility can be inferred from ingredient selection. These assumptions share a common error: properties of ingredients, formulations or regulatory status are treated as proxies for the behaviour of the finished product. Stability and microbiome science illustrate the consequences particularly well. Sensitive actives may degrade without obvious physical failure, while microbiome effects depend on the complete formulation, exposure pattern and target-site context. Regulatory compliance is essential but does not itself establish retention of every functionally relevant active throughout product life. We therefore argue for a finished-product perspective in which intended function, target-site biology, formulation architecture, packaging, storage and use conditions are treated as one integrated system and performance is verified at finished-product level using function-relevant methods under representative conditions of storage and use. Building on established systems-development principles, including Quality by Design, we term one approach to operationalising this perspective Function First: separating the starting opportunity from the primary design objective and optimising the complete product system around intended function.