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.
