What was the aim of this review?
To examine the effects of tea tree oil, an essential oil derived from an Australian tree, which can be applied in many different forms (eyelid wipes, eyelid shampoo, oil massages, etc.) on Demodex blepharitis. Demodex blepharitis is an inflammation of the eyelid caused by Demodex mites (frequently referred to as eyelash mites).
Key messages
We are uncertain if tea tree oil is better compared to other treatments. Other factors such as dosage, ocular hygiene, and patient compliance likely affect treatment outcomes; however, more and better-designed studies are needed to confirm these findings.
What did we study in this review?
Blepharitis causes symptoms such as eye itching, burning, dryness, irritation, watering, or blurry vision, which lead people to seek medical attention. This study aimed to understand the ability of tea tree oil to improve symptoms or to treat Demodex blepharitis (or both) in comparison to no treatment or other forms of treatment containing no tea tree oil.
What were the main results of this review?
This review included six studies with 562 participants (1124 eyes). They were men and women between the ages of 39 and 55 years. The included studies were conducted in the US, Korea, China, Australia, Ireland, and Turkey. Trial designs greatly varied, which limited analyses and the confidence in the results. Most studies included in this report had a high degree of bias. It is uncertain if tea tree oil (concentration ranging from 5% to 50%) is helpful for reducing the number of Demodex mites in people with Demodex blepharitis in short-term cases. While not fully addressed in the reviewed literature, people should be educated on how to properly apply tea tree oil products because patient compliance and method of application likely affects efficacy. None of the studies in this review reported any side effects directly related to the treatment; however, one study did report irritation around the eyes on using tea tree oil, which was resolved on re-educating the person on the application technique.
How up-to-date is this review?
Cochrane Review authors searched for trials that had been published before 18 June 2019.
The current review suggests that there is uncertainty related to the effectiveness of 5% to 50% tea tree oil for the short-term treatment of Demodex blepharitis; however, if used, lower concentrations may be preferable in the eye care arena to avoid induced ocular irritation. Future studies should be better controlled, assess outcomes at long term (e.g. 10 to 12 weeks or beyond), account for patient compliance, and study the effects of different tea tree oil concentrations.
Demodex blepharitis is a chronic condition commonly associated with recalcitrant dry eye symptoms though many people with Demodex mites are asymptomatic. The primary cause of this condition in humans is two types of Demodex mites: Demodex folliculorum and Demodex brevis. There are varying reports of the prevalence of Demodex blepharitis among adults, and it affects both men and women equally. While Demodex mites are commonly treated with tea tree oil, the effectiveness of tea tree oil for treating Demodex blepharitis is not well documented.
To evaluate the effects of tea tree oil on ocular Demodex infestation in people with Demodex blepharitis.
We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2019, Issue 6); Ovid MEDLINE; Embase.com; PubMed; LILACS; ClinicalTrials.gov; and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP). We used no date or language restrictions in the electronic search for trials. We last searched the databases on 18 June 2019.
We included randomized controlled trials (RCTs) that compared treatment with tea tree oil (or its components) versus another treatment or no treatment for people with Demodex blepharitis.
Two review authors independently screened the titles and abstracts and then full text of records to determine their eligibility. The review authors independently extracted data and assessed risk of bias using Covidence. A third review author resolved any conflicts at all stages.
We included six RCTs (1124 eyes of 562 participants; 17 to 281 participants per study) from the US, Korea, China, Australia, Ireland, and Turkey. The RCTs compared some formulation of tea tree oil to another treatment or no treatment. Included participants were both men and women, ranging from 39 to 55 years of age. All RCTs were assessed at unclear or high risk of bias in one or more domains. We also identified two RCTs that are ongoing or awaiting publications.
Data from three RCTs that reported a short-term mean change in the number of Demodex mites per eight eyelashes contributed to a meta-analysis. We are uncertain about the mean reduction for the groups that received the tea tree oil intervention (mean difference [MD] 0.70, 95% confidence interval [CI] 0.24 to 1.16) at four to six weeks as compared to other interventions. Only one RCT reported data for long-term changes, which found that the group that received intense pulse light as the treatment had complete eradication of Demodex mites at three months. We graded the certainty of the evidence for this outcome as very low.
Three RCTs reported no evidence of a difference for participant reported symptoms measured on the Ocular Surface Disease Index (OSDI) between the tea tree oil group and the group receiving other forms of intervention. Mean differences in these studies ranged from -10.54 (95% CI – 24.19, 3.11) to 3.40 (95% CI -0.70 7.50). We did not conduct a meta-analysis for this outcome given substantial statistical heterogeneity and graded the certainty of the evidence as low.
One RCT provided information concerning visual acuity but did not provide sufficient data for between-group comparisons. The authors noted that mean habitual LogMAR visual acuity for all study participants improved post-treatment (mean LogMAR 1.16, standard deviation 0.26 at 4 weeks). We graded the certainty of evidence for this outcome as low. No RCTs provided data on mean change in number of cylindrical dandruff or the proportion of participants experiencing conjunctival injection or experiencing meibomian gland dysfunction.
Three RCTs provided information on adverse events. One reported no adverse events. The other two described a total of six participants randomized to treatment with tea tree oil who experienced ocular irritation or discomfort that resolved with re-educating the patient on application techniques and continuing use of the tea tree oil. We graded the certainty of the evidence for this outcome as very low.