The spermacide (Nonoxynol-9) used in a number of those contraceptive devices and creams acts like a type of soap. So if you have a problem with soap staying on a sensitive mucous-producing spot of your skin for several hours, you may want to think twice about using a device that is embedded with soap.

Nonoxynol
Nonionic surfactant used as emulsifier, wetting & defoaming agent. Primary component in vaginal foams and creams (spermicidal).

Surfactant
Surface active agent that is able to mix water with oils. Chemicyll, there are 4 types of surfactants including anionic, amphoteric, non-ionic, and cationic surfactants. Basic ingredient in all soap-free personal cleansing products like cleansers, wetting agents, emulsifiers, solubizers, conditioning agents and foam stabilizers.

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SRS