Dry Eye Dx and Tx
Monitor Quality When Using Tea Tree Oil
BY KATHERINE M. MASTROTA, MS, OD, FAAO
My mother wore out her first copy of A Modern Herbal, The Medicinal, Culinary, Cosmetic and Economic Properties, Cultivation and Folklore of Herbs, Grasses, Fungi, Shrubs and Trees with All Their Modern Scientific Uses. First published in 1931, A Modern Herbal is a compendium of botanical drugs and preparations. Tea tree oil (TTO), produced by steam distillation of the leaves and terminal branches of Melaleuca alternifolia, is documented in A Modern Herbal. Used for more than 100 years medicinally, TTO has known antibacterial, antiviral, antifungal, antiprotozoal, and acaricidal activity (Gao et al, 2005). In fact, TTO has proven useful in treating Demodex (human follicle mite) blepharitis that is associated with ocular surface compromise (Kim et al, 2011).
Tea Tree Oil Usage
Brophy et al (1989) reported approximately 100 components of TTO and their range of concentrations. The main chemical components of TTO are terpinen-4-ol, y-terpinene, α-terpinene, 1,8-Cineole, α-terpinolene, α-terpineol, α-pinene, and p-Cymene. Most recently, Tighe et al (2013) demonstrated that Terpinen-4-ol, the most abundant ingredient in TTO, was more potent than TTO at equivalent concentrations and that terpinen-4-ol exhibited a synergistic effect with terpinolene, but an antagonistic effect with α-terpineol in killing Demodex mites—suggesting that terpinen-4-ol alone should enhance its acaricidal potency by reducing adverse and antagonistic effects from other ingredients in TTO.
Quality and Degradation
TTOs with high cineole content were thought to be of poor quality and more likely to cause skin irritation, as TTO can cause both irritant and allergic reactions; however, there is little scientific support for this notion. Rather, it has been observed that adverse reactions are primarily caused by oxidation that occurs in aged or improperly stored oil. TTO can undergo photo oxidation within a few days to several months, leading to degradation products that are moderate-to-strong sensitizers (Hausen et al, 1999).
Given the batch-to-batch variation, oil sold as TTO is regulated by the International Organization for Standardization (ISO), not the U.S. Food and Drug Association (FDA). For “Oil of Melaleuca-terpinen-4-ol type,” there is set a maxima and/or minima for 14 components of the oil. Notably, the standard does not stipulate the species of Melaleuca from which the TTO is sourced. Hence, oils that meet the requirements may have been distilled from Melaleuca species, of which there are approximately 230, other than M. alternifolia. Additionally, the physical characteristics of TTO present difficulties for the formulation and packaging of products. TTO is readily absorbed into plastics, and the composition of TTO may change considerably during storage. Light, heat, exposure to air, and moisture all affect oil stability, and product excipients may compromise its biologic activity. TTO should be stored in dark, cool, dry conditions, preferably in a vessel that contains little air.
Therefore, I suggest prudence to those practitioners compounding TTO mixtures in office for patient therapy, as there are relevant data gaps in such practice. It is my personal preference to invest in commercially prepared products formulated for use around the adnexa and ocular surface to avoid significant iatrogenic complications. CLS
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Dr. Mastrota is Secretary of the Anterior Segment Section of the American Academy of Optometry. She is a consultant or advisor to Allergan, B+L, BioTissue, Nicox, and OcuSoft and is a stock shareholder of TearLab Corporation. Contact her at email@example.com.