A method for the reduction in the risk of transmitting a sexually transmitted disease—especially HIV and/or HSV—during sexual activity is provided. This method generally comprises the application of an effective amount of an inhibitory agent, preferably as a topical formulation, to the area or areas of sexual contact prior to engaging in sexual activity. Inhibitory agents which are useful in the present invention include, for example, phosphorylated hesperidins, sulfonated hesperidins, polystyrene sulfonates, substituted benzenesulfonic acid formaldehyde co-polymers, H2SO4-modified mandelic acids, and the like. This method can be used by heterosexuals, homosexuals, and/or bisexuals engaged in a wide variety of sexual activities. In addition to anti-STD activity, these agents may also act as vaginal contraceptives; moreover, they generally have fewer side effects than conventional vaginal contraceptives (e.g., nonoxynol-9). For example, the compounds useful in this invention are generally not toxic to natural and beneficial vaginal flora and, thus, do not upset the local microbiological balance. The anti-STD method of the present invention has the added advantage that it can be implemented and controlled by either sexual party. Methods are also provided for reducing the risk of transmission of STD-causing organisms to health care providers and laboratory personnel (or other persons) who may come into contact with biological samples and specimens.