Glycerol and ichthammol: medicinal solution or mythical potion?

Glycerol and ichthammol (G & I) has been used for generations by otologists. However, there is a paucity of information on both its mode of action and its anti-bacterial properties. The aim of this paper was to ascertain firstly, what the most common organisms found in discharging ears were and secondly, what antibacterial activity G & I had against these organisms. All ear swabs from 1992-1994 in our unit were reviewed to ascertain the prevalence of the commonly isolated organisms. Fresh isolates of these organisms were collected and plated onto agar with wells of glycerol, ichthammol and a combination of both as used in clinical practice. The diameters of the zones of inhibition observed after incubation were measured in millimetres. Common isolates were: Pseudomonas aeruginosa, Staphylococcus aureus, Proteus mirabalis, Streptococcus pyogenes in descending order of frequency. Pure glycerol showed no significant zones of inhibition against any of the organisms tested. The average zones of inhibition for G & I and ichthammol alone were for Staphylococcus aureus 15 mm and 18 mm and for Streptococcus pyogenes: 16 mm and 23 mm. Ichthammol alone was significantly more effective than G & I (p < 0.001). There was no significant activity against Proteus mirabalis and Pseudomonas aeruginosa. The therapeutic benefit of G & I is due in part to the inherent anti-bacterial activity of ichthammol against the Gram positive organisms as well as its anti-inflammatory action and the dehydrating effect of the glycerol.