Assessment of ototoxicity of tea tree oil in a chinchilla animal model

Abstract

Objective

The aim of the present study is to examine the effects of tea tree oil on hearing function and cochlear morphology after intratympanic administration in a chinchilla animal model.

Methods

Nine chinchillas received intratympanic injection of 3% tea tree oil dissolved in olive oil in one ear, whereas the contralateral control ear received olive oil only. Outcome measures included auditory brainstem responses conducted before treatment and at 10 days and 30 days following the injection. Post-mortem cochlear morphology was assessed using scanning electron microscopy.

Results

At 10 and 30 days following the injection, there was no significant change in auditory brain response thresholds at 8, 16, 20 or 25 kHz. Scanning electron microscopy imaging showed no damage to auditory hair cells.

Conclusion

Tea tree oil (3%) does not appear to be ototoxic in a chinchilla animal model. Future preclinical and clinical studies are required to establish the effectiveness of TTO in treating otitis.

Introduction

Otitis media is the most frequent diagnosis in children and also the most common infection for which antibiotics are prescribed for Refs. [1], [2], [3]. A tympanic membrane perforation is a well-known complication observed in 4.5–7% of children diagnosed with otitis media [4], [5]. In the presence of such perforation the risk of solutions administered in the ear canal entering into the middle ear greatly increases, thus raises the concern for ototoxicity.

Non-antibiotic approaches for infection treatments and pain reduction are becoming increasingly common and favored by parents and some health professionals [6]. When appropriate, alternatives to antibiotics are being considered to treat otitis, especially in children to prevent bacterial resistance. For many years, essential oils have been used as substitutes to medication [7]. Tea tree oil (TTO) is an essential oil derived from the leaves of Melaleuca alternifolia found in Australia. The medicinal properties of TTO were first reported by Penfold in the 1920s and since then have been thoroughly examined by numerous in vitro studies and in vivo [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20]. These studies provide conclusive evidence supporting the antibacterial, antifungal, antiviral and anti-inflammatory properties of TTO.

Given that many of the pathogenic organisms responsible for otitis externa could fall within the TTO antimicrobial spectrum, Farnan et al. conducted an in vitro study assessing the susceptibility of organisms to TTO using swabs taken from patients’ ears with otitis externa [21]. The study concluded that TTO might be an efficient alternative choice for the treatment of otitis externa.

Since TTO does not require a prescription, it can be used by individuals who may be unaware of the condition of their tympanic membrane. This study was conducted to assess the ototoxicity of TTO after intratympanic administration in a chinchilla model.