# Viper Venom and Synthetic Peptides: Emerging Active Ingredients in Anti-Ageing Cosmeceuticals
## 2 Peptides--From Snake Venom to the Cosmetic Industry  
Among many aspects that contribute to the well-being of consumers, healthy and youthful-looking skin plays a very important role, considering the market growth for skin care products observed in recent years [25]. Ageing is a time-dependent biological process, with its earliest signs gradually appearing as progressive changes in the skin's morphology and physiology. Skin is the largest organ of the human body, and its functions are various physiological processes, such as thermoregulation, vitamin D production, sensory perception and, most importantly, protection against external factors [7]. As the skin plays a central role in personal identity, consumers increasingly seek solutions to counteract the ageing process, showing a strong preference for anti-ageingcosmetics formulated with innovative active ingredients. The use of bioactive or functional compounds of natural origin remains a prevailing trend. Beyond efficacy, growing environmental awareness is also influencing formulation strategies, with a clear shift toward reducing the reliance on synthetic ingredients in favor of more sustainable alternatives [7]. Natural products are based on derivatives of organisms found in nature, such as algae, plants and animals. These include proteins, peptides, carbohydrates, minerals, antioxidants, essential fatty acids, vitamins or fibers. The different categories of natural anti-ageing ingredients include moisturizers, barrier repair agents, antioxidants, vitamins, hydroxy acids, anti-inflammatory and sunscreen ingredients [7; 26]. Peptides are important in many natural processes relevant to skin care, such as modulation of cell proliferation, cell migration, inflammation, angiogenesis and protein synthesis and regulation, leading to a wide variety of physiological processes, including defense, immunity, homeostasis and reproduction [21; 27]. Biomimetic peptides, on the other hand, are compounds that have an amino acid sequence identical to physiological peptides, which are biotechnology synthesized. They mimic the action of growth factors and cytokines by interacting with their receptors, leading to clinical effects such as preventing the visible signs of skin ageing [28]. Bioactive peptides are also synthetic compounds consisting of modified amino acid chains that improve an already existing physiological function, such as increased skin permeability, stability, solubility and better interaction with cell receptors. Also, several natural physiological processes are modulated by interaction with a specific amino acid sequence found in peptides and protein fragments. Thus, bioactive peptides are becoming increasingly promising in cosmetic products, with clinical applications in various skin conditions [28]. Multiple applications of these synthetic compounds, either biomimetic or bioactive, through topical application, offer treatment options for the prevention or alleviation of the clinical aspects of dysfunctional skin, such as ageing, hyperpigmentation and wrinkle development. They can stimulate collagen and elastin synthesis, enhance wound healing, increase fibroblast proliferation, but also possess antioxidant, antimicrobial and whitening effects [28; 29]. Peptides have been used in the cosmetic industry since 1973, when [PERSON] proposed the synthetic peptide GHK (glycyl-L-histidyl-L-lysine) as a signal peptide that enhances collagen production and acts as a carrier peptide when coupled with Cu (II). However, they did not gain notoriety in cosmetics until the early 2000s, when Palmitoyl Pentapeptide-4 was launched, proposing to reduce facial wrinkles. Since then, due to their versatility, several peptides of cosmeceutical interest have emerged, being developed according to consumer demands [25; 30]. Based on their capability to control certain biological functions, nowadays, peptides are one of the latest advanced ingredients that have led to a beauty revolution [31].