Melaleuca alternifolia (tea tree) oil gel (6%) for the treatment of recurrent herpes labialis

Extract

Sir,

Recurrent herpes labialis (RHL) or cold sores affect 20–40% of the population, some of whom develop frequent attacks.¹ Systemic therapy with aciclovir, valaciclovir or famciclovir can suppress or shorten the duration of attacks,² although the cost of these agents restricts their availability. Topical therapy with aciclovir is popular, although studies assessing the effects of treatment have yielded inconsistent results.³ The essential oil of Melaleuca alternifolia, or tea tree oil (TTO), has broad-spectrum antimicrobial activity in vitro,⁴ including activity against herpes simplex virus (HSV),⁵ the aetiological agent of RHL.

We undertook a pilot study to evaluate the efficacy of topically applied TTO in the treatment of RHL. A randomized, placebo-controlled, investigator-blinded protocol was used. Double-blinding was not attempted because of the distinctive odour of TTO. Patients aged 18–70 years with a self-reported history of recurrent RHL were recruited. Exclusion criteria included antiviral therapy in the previous month, long-term steroid therapy, immunocompromised status, pregnancy, lactation or known allergy to TTO. The protocol was approved by the local institutional review board and informed written consent was obtained from each patient. Participants presented as soon as possible after onset of an attack and were randomized to receive either 6% TTO in an aqueous gel base or placebo gel (Australian Bodycare Pty. Ltd, Mudgeeraba, QLD, Australia). Patients applied the gel five times daily, recorded treatment applications and adverse events in a daily diary, and were assessed daily (except Sunday) in the clinic, where swabs were collected for HSV detection by PCR and culture. Visits continued until re-epithelialization occurred and PCR was negative for HSV DNA on two consecutive days. Patients did not apply the gel 3 h before their visit to minimize carry-over onto swabs for HSV detection and to maintain blinding of the investigators. The parameters measured were time to re-epithelialization, time to crust formation, duration of virus detection by PCR and culture, and virus titre. The duration of each parameter was measured from the time the patient first noticed their lesion and results compared using the Mann–Whitney test.