Abstract The historical background, rational and experimental evidence for the presence and function of a “gastric barrier” has been reviewed. In vitro and in vivo experiments were carried out to determine the effect of pH on common CSF shunt infecting organisms. A critical pH level of 3.5–3.8 has been established for a successful kill rate after 15 min of exposure, documenting the barrier theory to be a function of pH and time of exposure. The use of low pH supplement feedings (Coca Cola and ginger ale) is feasible and may be desirable. Some possible disadvantages when employed clinically are enumerated.