The cerumen produced by the ceruminous glands of canine ears is a complex mixture of exfoliated cells, waxes, oils, free fatty acids, esters, immunoglobulins, and proteins. In a healthy ear, no cleaning is needed. When ear disease is present, cerumen production increases and removal is needed to minimize irritation, prevent perpetuation of the disease, allow topical otic medications to contact the epithelium, and help establish a normal environment. In this study, 13 ear cleaners were evaluated with a standardized synthetic cerumen that mimics canine cerumen. Each of the cleaners was incubated for 20 minutes with the artificial cerumen and activity measured by decantation. The incubation process was designed to mimic the conditions in a dog's ear (test tubes were used), mild agitation (head shaking) was provided, and the incubation process was conducted at near body temperature. In this study, only 4 products were able to remove all or part of the cerumen plug in the test tube. Efficacy of the four products was 86% to 90% for one, followed by 39%, 23%, and 8% for the other three; the rest of the products tested showed no activity. The most efficacious product contained salicylic acid, lactic acid, oleic acid, propylene glycol, neutral salicylic esters, neutral benzoic esters, and benzoic acid. The first ingredient in the next 2 most efficacious products was menthol. Study sponsored by Laboratorios Dr Esteve S.A.

COMMENTARY: This study was conducted on products from Europe; however, for veterinarians in the United States there are several important take-home points. First, these investigators developed a reproducible model for testing the ceruminolytic activity of ear cleaners. Before this study, most reports were based on clinical trials, anecdotal recommendations, or product literature from the manufacturer. This methodology allows for a controlled, blinded study method. Second, veterinarians and clients invest a great deal of money in the purchase of ear cleaners, and this study showed that most available products lack efficacy. It would be interesting to repeat this study on products marketed in the United States. Finally, based on these findings, veterinarians should look for commercial products with compositions similar to the one the investigators found to have the most activity.

In vitro investigation of ceruminolytic activity of various otic cleansers for veterinary use. Sanchez-Leal J, Mayos I, Homedes J, Ferrer L. VET DERMATOL 17:121-127, 2006.