In an embodiment, a barrier-forming composition includes a carbohydrate gum, a humectant, and an antimicrobial agent. The composition furthermore meets the following requirements: about 0.01% ≤ C ≤ about 0.4%; about 4.5% ≤ H ≤ about 65%; and 0.050% ≤ A; or about 0%≤ C <; about 0.4%; about 55% ≤ H ≤ about 65%; and 0.050% <; A. C is the carbohydrate gum; H is the humectant; and A is the antimicrobial agent. All percentages are by weight of the total composition. In an embodiment the barrier-forming composition has an Rf value in water of 0 to about 0.25. A method of making and administering the barrier- forming composition to block, neutralize, or kill microorganisms is also provided.