## 1 Introduction
In addition, allantoin stimulates epidermal granulation in the wound-healing process by stimulating fibroblast proliferation and ECM production [14; 16; 17]. Glycolic acid, one of the main representatives of \(\alpha\)-hydroxy acids, has a low molecular weight, as well as good water solubility, making it easy to penetrate the basal layer [18; 19]. Its application in the treatment of mature skin stimulates fibroblast proliferation, collagen production, restoration of elastic fibers, and normalization of the thickness of the epidermal layers. In addition, it evens out skin tone, reduces hyperpigmentation, and makes the skin smooth and firm [20; 21]. Lactic acid is well soluble in water. Because of its larger molecule, the compound penetrates less into the deeper layers of the epidermis. It has found use in reducing hyperpigmented lesions and acne scars, as well as in the care of sensitive skin and mature skin showing signs of dryness. A corollary of the action of lactic acid is the acceleration of keratinization of the upper layers of the epidermis and the stimulation of keratinocytes for cell division [22; 23; 24]. The positive effect of snail mucus on slowing skin aging may also be evidenced by its effect on the synthesis of MMPs and the presence of protease inhibitors associated with inhibiting the activity of proteolytic enzymes responsible for collagen degradation [6; 25]. For the anti-aging effect of preparations containing snail mucus, the content of glycosaminoglycans in the mucus is also important. These compounds maintain the structural integrity of the intercellular substance of the tissue, which, thanks to them, obtains the appropriate elasticity and resilience. The participation of these macromolecules is essential for proper cell organization, function, migration, and growth regulation [26]. Glycosaminoglycans attract cations, such as Na+, which exhibit strong osmotic activity, allowing them to bind significant amounts of water in the intercellular substance, at the same time forming a reserve of water in the skin [26; 27; 28]. The use of raw materials with multidirectional effects on the skin is further associated with the search for the most effective methods of introducing these compounds into the deeper layers of the skin, including needle-free and micro-needle mesotherapy treatments. In needle-free mesotherapy, the treatment methodology uses physical stimuli, including electroporation, whose role is to promote the transport of active ingredients and drugs into the cell. The effect of short high-voltage electrical pulses induces a temporary destabilization of the cell membrane, allowing the transport of active macromolecules from the intercellular space into the cell [29; 30]. Micro-needle mesotherapy, on the other hand, is a procedure during which controlled mechanical damage is performed through micropunctures to selected areas of the skin, using thin needles. Micro-needling leads to an increase in the cell's membrane potential and its secretory activity of, among other things, proteins, macronutrients, and growth factors into the intercellular space, stimulating natural mechanisms of skin regeneration [31]. The main aim of this study was to evaluate the effect of preparations containing _Helix aspersa_ snail mucus on skin regeneration with photoaging features. In addition, the aim of the current study was to compare the effectiveness of different methods of mesotherapy: (A) micro-needling with a formulation containing 98.2% snail mucus; (B) micro-needling with a 0.9% NaCl solution; (C) needle-free with a formulation containing 98.2% snail mucus.