Otologic safety of manuka honey

To investigate the possible ototoxic effects of a 50% concentration of manuka honey in a chinchilla animal model.

A prospective, controlled animal study.

The Research Institute of the Montreal Children's Hospital, McGill University Health Centre.

Eight animals had myringotomy incisions in both ears. One ear was randomly assigned to receive the 50% manuka honey solution. The contralateral ear received saline and served as the control ear.

Auditory brainstem evoked responses (ABRs) were measured bilaterally for a wide range of frequencies (between 8 and 25 kHz) before and 2 weeks after transtympanic manuka honey and saline application. The animals were sacrificed, and all cochleae were dissected out and processed for light and scanning electron microscopy (SEM).

The measured ABR thresholds after the application of 50% concentration of manuka honey revealed severe ototoxicity in all honey-exposed ears. This was accompanied by gross physical changes and histologic evidence of hair cell toxicity on SEM and light microscopy. The control ears remained unchanged during the period of the experiment.

Although 50% concentration of manuka honey is the proven concentration to have bactericidal properties against biofilms of Pseudomonas aeruginosa and Staphylococcus aureus, this concentration appeared to have caused severe or intense inflammatory changes that produced facial paralysis, vestibulotoxicity, and hearing loss.