Several studies have been conducted using zinc compounds that were either insoluble and released no Zn²⁺ ions, or were soluble but had a high stability constant and released essentially no ZnZn²⁺ ions at pH 7.4. No effect upon the duration or severity of common colds was noted using neutrally charged zinc compounds. These lozenges are representative of several health-food store products being marketed ostensibly for nutrition benefit in common colds, without benefit of a New Drug Application or any documentation.