When formulating with surfactants, synergism is our best friend to build viscosity and to achieve a specific application performance. The “classic” and most popular synergy when it comes to forming worm-like micelles for rheology control is the one between SLES (INCI: Sodium Laureth Sulfate) and CAPB (INCI: Cocamidopropyl Betaine), combined with the addition of salt. Less well-known is why this formulation principle also has inherent benefits when it comes to foaming performance. It will be explained how the foamability of such formulations is related to the rheology (to be more specific: the normal force at high shear rates) of dilutions of the formulation. The situation pretty much changes when replacing SLES by greener, i.e. biobased surfactants or even biosurfactants, containing carboxylate instead of sulfate as anionic group. Since the synergism mentioned above ceases to work in these cases, the typical salt curve is not an option anymore. Instead, one can use a pH variation to build viscosity. It will be shown how this alternative option can be used for rheology control – and why this concept leads to challenges in terms of foaming performance. In conclusion, in the development of more sustainable and milder, sulfate-free formulations, an understanding of the physical chemistry beyond the established synergies is crucial.