## 8 Bromelain, Ficin, and Papain Peels By-Products-Based Cosmetic Applications  
Protcolytic enzymes like bromelain, ficin, and papain are widely used in cosmetics due to being able to break down proteins, facilitate exfoliation, and enhance skin renewal. They provide a gentler, yet equally effective, alternative to traditional mechanical and chemical exfoliants, rendering them ideal for a diverse range of skincare, haircare, and generally dermatological applications. Such enzymes have been or may be integrated in enzyme peels, masks, exfoliating cleansers, scrubs, anti-wrinkle creams and serums, acne spot treatments, oil control masks and toners, dandruff or scalp exfoliating shampoos, scalp serums treatment, foot peels, and hand and cuticle treatments, as well as many other cosmetic products and cosmeceutical formulations. Bromelain is commonly used in exfoliating masks, cleansers, and anti-inflammatory creams, ficin is preferred in mild exfoliants for sensitive skin, and papain features in deep exfoliators [18, 45, 52, 155, 156]. Proteolytic enzyme-based formulations have provided great benefits and efficacy in skincare, such as gentle exfoliation. Bromelain, ficin, and papain effectively degrade keratin _stratum corneum_-located proteins, facilitating the removal of dead skin cells without causing significant irritation. They are non-abrasive and gentle on the skin, and are thus ideal for acne- or rosacea-prone skin and do not cause over-exfoliation. Therefore, they are suitable for sensitive skin types that may react negatively to harsh exfoliants [22, 27, 157]. Also, such enzymes exhibit anti-inflammatory effects by inhibiting pro-inflammatory cytokine activity, reducing excessive immune activation. By breaking down swelling-inducing proteins, damaged peptides, and other skin inflammatory mediators, they can reduce inflammation and fluid accumulation. Proteolytic enzymes promote collagen formation and enhance the skin barrier without interfering with its natural defense system [26, 42]. The systemic usage of products containing bromelain, ficin, or papain can lead to a more even skin tone and an improved texture. Such proteolytic enzymes remove melanin-rich keratinocytes (pigmented dead skin cells), but they also slow melanin production, preventing new dark spots and, therefore, targeting hyperpigmentation. By inhibiting enzymes involved in melanin production, they lighten age spots, acne scars, and even sun damage, leading to a more uniform complexion. They also help smooth out rough areas of the skin caused from clogged pores, dead skin accumulation, or uneven collagen structure, leading to smoother, softer skin with fewer breakouts [18, 156]. The enhanced absorption of active ingredients is also observed. By exfoliating the outer layer of dead skin cells, proteolytic enzymes modulate the skin's permeability, allowing larger or complex molecules penetration. Enhanced penetration leads to the better absorption of other active constituents in skincare-based products, and since the bioavailability of key ingredients is improved, skincare and haircase treatments show better efficacy [27, 46, 94]. Enzyme-based hair and scalp care has also been investigated. Since they dissolve excess keratin buildup, bromelain, ficin, and papain can reduce scalp flakiness, dandruff, and/or scalp irritation. Such enzymes may gently exfoliate the scalp, preventing clogged hair follicles, boosting hair growth, strengthening hair strands, and promoting overall hair follicle health [27, 46, 94]. Moreover, considering wound healing and scar reduction, the proteolytic activity of these enzymes is beneficial by debriding necrotic tissue; decreasing redness, irritation and pain; stimulating collagen formation; and consequently, promoting the formation of new, healthy tissue. They can also help in reducing scar appearance, accelerating the healing process, and improving overall skin health [147, 158, 159, 160, 161], as observed in post-surgery healing ointments and creams for after-burn treatment [162].