## 1 Introduction  
The quest for healthy, radiant skin has driven significant advancements in cosmetic science, leading to the emergence of various groundbreaking cosmetics. Exfoliation is an essential part of skincare, as it promotes skin renewal. Natural exfoliants made from fruits and dairy products have always been used in skincare, implying that bioactives play an important role in skin health. Ancient civilizations such as the Egyptians, Mesopotamians, Chinese, and Greeks, used natural substances like milk, honey, and fruits for skin rejuvenation. For example, [PERSON] bathed in sour milk, which was known to be acidic, an action which foreshadowed more targeted enzyme treatments [1,2]. Modern commercial exfoliants appeared during the 19 th century and contained ground nutshells, pumice, or other abrasives, while chemical exfoliants started a new era, offering a gentler alternative to traditional exfoliation. Nowadays, enzyme-based exfoliants are prominent in the cosmetic industry, and exfoliation is an effective method in skincare routine, globally [1,3,4,5]. Skin exfoliation is a process that involves removing dead (non-vital-keratinized) cells and impurities from the surface of the skin, aiding in skin cell renewal. Eliminating this layer from the skin makes the _stratum corneum_, namely the outermost skin layer, more uniform, improves skin texture and homogeneity, prevents clogged pores and dullness, and improves the skin's overall appearance. The active ingredients of other cosmetic or dermatological products are also more capable of penetrating skin barriers [5, 6, 7, 8, 9]. Three possible depths exist concerning exfoliation: superficial (60 \(\upmu\)m from the _stratum corneum_, until the papillary dermis, impacting the epidermis and _plexus superficialis_), medium (450 \(\upmu\)m from the papillary dermis up to the reticular dermis, also interacting with _plexus superficialis_) and deep (from mid-reticular dermis and up to 600 \(\upmu\)m, including the _plexus profundus_ above the subcutaneous fat) (Figure 1) [1,5,6,10,11]. Superficial exfoliation removes the outermost layer of dead skin cells improving overall texture, while preparing the skin for an efficacious absorption of skincare products. Medium-depth exfoliation is performed to reduce fine lines, hyperpigmentation, acne scars, and uneven tone. Finally, deep exfoliation treats severe scarring, deep wrinkles, and sun damage, while promoting collagen production. The depth of exfoliation caters to a wide range of skincare needs, from everyday maintenance to intensive corrective treatments [1,5,6,12]. All exfoliation methods used can be broadly categorized into physical and chemical, each serving different skin needs. Physical exfoliation (or mechanical) is the most  
Figure 1: Schematic illustration of the main skin layers, as well as bromelain, ficin, and papain peel by-products’ molecular structure, exfoliating properties, and sustainability in cosmetic applications. (Parts of this figure were obtained from the free databases: [[https://smart.servier.com/](https://smart.servier.com/)]([https://smart.servier.com/](https://smart.servier.com/)), [[https://www.rcsb.org/](https://www.rcsb.org/)]([https://www.rcsb.org/](https://www.rcsb.org/)) and [[https://www.freepik.com/](https://www.freepik.com/)]([https://www.freepik.com/](https://www.freepik.com/)) (accessed on 27 January 2025)). traditional exfoliation way, and relies on physical abrasion to slough off dead skin cells. Such products have abrasive particles, like microbeads, sugar, coffee grounds, salt, or fruit kernels. Specifically, for physical exfoliation, certain tools such as brushes, special sponges, and dermaplaning razors may also be used [5; 8; 13; 14; 15; 16]. Chemical exfoliation relies on many chemical agents (i.e., \(\alpha/\beta\) hydroxy acids or enzymes), which exfoliate the skin due to their acidic character that dissolves bonds between dead skin cells [5; 8; 13; 14; 15; 16].