Swallowing disorders, or dysphagia, is a growing problem especially as the population gets older. Fluid thickening is a well-established strategy for treating dysphagia, but the effects of thickening on the physiology of impaired swallowing are not fully understood and the relations to basic rheology are scarce. Commercial thickeners studied showed different behavior in both shear thinning, yield stress and first normal stress difference, and even larger differences in extensional viscosity.