Nanoemulsions are being increasingly utilized in the pharmaceutical, cosmetics, and food industries. They have gained special attention in the cosmetic sector owing to their smaller size and higher kinetic stability and their ability to improve the cutaneous penetration of active ingredients. In addition, they reduce transepidermal water loss, which augments the skin's barrier function. In recent years, the increased awareness among consumers about the health-linked benefits of natural ingredients in cosmetics has urged finding green cosmetic ingredients that are benign to the skin. One of the natural motivations for this quest is finding suitable emulsifier candidates with negligible side effects that are sourced from plants or microbes, which can serve as viable replacements to the erstwhile used synthetic surfactants. Formulating a stable nanoemulsion system for cosmetic application entails a systematic understanding of important attributes of the surfactant candidate such as critical micelle concentration, hydrophilic lipophilic balance, critical packing parameter, and Winsor ratio that are pivotal to the overall performance of the emulsion system. The current review attempts to portray the salient features of nanoemulsion systems in cosmetic formulations, by essentially capturing the important characteristics of the emulsifier that dictate the overall stability of a nanoemulsion system. The recent transition toward the use of green ingredients such as emulsifiers and oils that are dermatologically safe has been delineated, by highlighting their important properties. Furthermore, the progress made so far in the application of microbial biosurfactants in nanoemulsion formulations is presented. Finally, the factors that dictate the overall stability of the nanoemulsion are briefly reviewed.

中文翻译：

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用于化妆品应用的绿色纳米乳液综述，特别强调微生物表面活性剂作为即将到来的乳化剂

纳米乳液越来越多地用于制药、化妆品和食品工业。由于其较小的尺寸和较高的动力学稳定性以及它们改善活性成分皮肤渗透的能力，它们在化妆品领域获得了特别的关注。此外，它们还能减少经皮水分流失，从而增强皮肤的屏障功能。近年来，消费者对化妆品中天然成分与健康相关的益处的认识不断提高，这促使人们寻找对皮肤无害的绿色化妆品成分。这一探索的自然动机之一是寻找来自植物或微生物的副作用可忽略不计的合适乳化剂候选物，它们可以作为过去使用的合成表面活性剂的可行替代品。配制用于化妆品应用的稳定纳米乳液系统需要系统地了解表面活性剂候选物的重要属性，例如临界胶束浓度、亲水亲油平衡、临界填充参数和温莎比，这些对乳液系统的整体性能至关重要。目前的综述试图通过从本质上捕捉决定纳米乳液系统整体稳定性的乳化剂的重要特性来描绘化妆品配方中纳米乳液系统的显着特征。通过强调它们的重要特性，已经描述了最近向使用对皮肤病学安全的绿色成分（如乳化剂和油）的过渡。此外，介绍了迄今为止在纳米乳液配方中应用微生物生物表面活性剂方面取得的进展。最后，简要回顾了决定纳米乳液整体稳定性的因素。