SALICYLIC ACID

Salicylic acid reduces viral numbers by mechanical removal of infected tissue. It also stimulates production of protective antibodies in response to the mildly irritant effect of the acid.

It is a constituent of several wart and verruca treatments, in concentrations varying from 11-50 per cent, alone and in combination with other constituents. Presentations include gels, ointments, plasters and collodion-based paints. They are applied either daily, two to three times weekly or once a week, depending on formulation.

Dead skin tissue is filed off with an emery board between applications. Treatment may be necessary for up to 12 weeks.

LACTIC ACID

Lactic acid has antiseptic and caustic properties and enhances the bioavailability of salicylic acid from formulations in which it is included, in strengths of 4 per cent in gels and 16.7 per cent in collodions. It is corrosive and care must be taken that preparations do not spread onto unaffected skin.

FORMALDEHYDE

Formaldehyde 0.75 per cent gel has antiviral activity and also a direct anhidrotic action, drying verrucas, for which indication it is particularly recommended, as well as surrounding skin. It requires twice daily application.