Soaps containing an abrasive were developed primarily to aid in removing grease and other heavy dirt from the skin. These products have been made with many different abrasives, such as coarse sand, finely pulverized pumice, bentonite, sawdust and oatmeal. There is evidence that the coarse, hard materials (sand) may damage the skin if used repeatedly, while oatmeal and similar soft substances apparently add little to the mechanical cleansing action of the soap. Between these two extremes lie materials sufficiently hard to enhance cleansing by abrasion yet so finely ground that they are safe for the skin.
There are relatively few references in the literature to the effects of abrasive soaps on the skin. In a recent review, Klauder, Gross and Brown1 reported on the examination of some forty-four brands of mechanics' soaps and stated (page 342): "Most writers advise against the use of abrasive (grit soaps)." As
ROY L. KILE, ASHTON L. WELSH. CLINICAL OBSERVATIONS ON THE USE OF SOAPS CONTAINING AN ABRASIVE. Arch Derm Syphilol. 1944;49(3):188–189. doi:10.1001/archderm.1944.01510090034006