Deactivation
Chlorhexidine is deactivated by anionic compounds, including the anionic surfactants commonly used as detergents in toothpastes and mouthwashes, anionic thickeners such as carbomer, and anionic emulsifiers such as acrylates/C10-30 alkyl acrylate crosspolymer, among many others. For this reason, chlorhexidine mouth rinses should be used at least 30 minutes after other dental products. For best effectiveness, food, drink, smoking, and mouth rinses should be avoided for at least one hour after use. Many topical skin products, cleansers, and hand santitizers should also be avoided to prevent deactivation when chlorhexidine (a topical itself or the residue from a cleanser) is meant to remain on the skin.
The rival chemical PCMX does not have this issue or the warnings about eye & middle-ear contact, though it is usually less potent in the form and concentrations normally used.
Although chlorhexidine is effective in the presence of blood, real soap, and pus, its activity is reduced.
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