The development of personal care formulations incorporates the deliberation of the prerequisite product rheology and the right rheology modifier to deliver these effects. While the effectiveness of the finished product will hinge on the selection and level of active ingredients and excipients, the esthetics and even the penetration of these actives into the stratum corneum will be affected by the product rheology. Rheology modifiers are frequently denoted as thickeners, and while increasing the apparent viscosity should enhance the perception of quality in a formulation, this is only one aspect of rheological control. The product itself can be Newtonian or pseudoplastic, thixotropic, existing as a ringing gel or a stringy flowable liquid. This changes the way that the product appears in the bottle, the ease with which aliquots are poured or scooped from the packaging, the process of rubbing it into the skin or along the hair shaft, and upon using, the rinsing and removal of the product. It will also be vital to select the correct rheological characteristics to guarantee the stability of the finished formulation. By changing the structure of polymeric rheology modifiers, the impact on the sensorial properties and performance characteristics can be investigated. Careful selection of monomers, structure and other co-ingredients will result in products optimized for use in skin care formulations. Copyright (c) 2016 John Wiley & Sons, Ltd.