The objective of this educational article is to explain in non-technical terms how the engineering considerations in the design of prophylactic dressings for pressure ulcer (PU, also known as pressure injury) prevention eventually determine the associated clinical and cost-benefit outcomes. The article specifically describes a bioengineering algorithm for quantitative evaluation of the biomechanical efficacy of different prophylactic dressing designs, which is exemplified for two fundamentally different dressing technologies, one based on superabsorbent cellulose core versus the conventional silicone-foam dressing design. A set of three biomechanical indices is described and employed for the above comparative evaluation, namely, the protective efficacy index, the protective endurance and the prophylactic trade-off design parameter. It is demonstrated that the dressing with the superabsorbent cellulose core is at least as good as silicone-foams but, importantly, provides a good balance between its protective performance in its 'new' condition, as opposed to its 'used' condition, i.e., after being exposed to moisture. Most notably, we show that preventative dressings are never equal in their performances; the underlying structure and the dressing ingredients together determine the extent of the delivered tissue protection and its durability.