A hand sanitizer (2) comprises: (a) a first part comprising a chlorite in an alcoholic medium having a first foam promoter dissolved therein and contained in a first foam dispenser (4) whereby it is dispensed as a first foam; and (b) a second part which comprises an acid in an alcoholic medium which has a second foam promoter dissolved therein and which is contained in a second foam dispenser (6) whereby it is dispensed as a second foam; wherein the chlorite and the acid will react to provide chlorine dioxide when the first foam is mixed with the second foam; and wherein a mixture (18) of equal quantities of the first part and the second part contains at least 50% alcohol by weight.