## 3 Discussion
The study conducted on skin fibroblast culture shows that donkey milk may be useful in the treatment of inflammatory skin diseases as well as in wound healing, regenerative, and aesthetic dermatology [24]. Mare's colostrum, especially its fat fraction [25] and bovine colostrum [26], strongly stimulates the proliferation of fibroblast culture. It is believed that they may affect the effectiveness of skin wound healing. The _in vivo_ wound healing ability of multifunctional bovine colostrum-conjugated nanofibrous dressings was confirmed in a rat wound model. Probably, high levels of immunoglobulins, lactoferrin, hormones, and cytokines played a significant role in wound healing [27]. Consideration should also be given to reports on the oral supplementation of dairy substances and products. Routine four-week intake of fermented milk products loaded with various lactic acid bacteria strains resulted in increased skin hydration [28]. Other evidence suggests that continuous supplementation with sphingomyelin (SM), a phospholipid found in milk fat globules, has the potential to boost skin hydration and elasticity [29]. An oral formula with high levels of milk proteins, growth factors, alpha-lactalbumin, lactoferrin, and immunoglobulins was found to diminish skin lesions in individuals with plaque psoriasis [30]. The same proteins are present in sheep colostrum [3]. An oral administration of bovine lactoferrin prevented transepidermal water loss, irregular epidermal thickening, cell apoptosis, and increased skin hydration in UVB-radiated hairless mice [31]. Many of the health-promoting effects on human skin have been attributed to the vitamins, minerals, and amino acids present in bovine colostrum [32]. Collagen production, wound healing, and antioxidant activity are believed to be supported by ascorbic acid (vitamin C), niacin (B3), biotin (B7), vitamin E, and retinol (A), while minerals like zinc and copper contribute to neutralizing free radicals and tissue regeneration. In addition, various amino acids, such as proline, threonine, methionine, and arginine, also promote skin health by supporting anti-aging and wound healing activities [32]. It is also important to emphasize that sheep colostrum is as rich in minerals as bovine colostrum, and richer in protein [3]. Although toxicological studies on our raw material, sheep colostrum, have not been assessed, they were carried out on colostrum of bovine origin. Toxicological evaluations of an ultrafiltered bovine colostrum product, i.e., a mixture of native colostrum and a unique subset of concentrated low-molecular-weight proteins (\(\leq\)10 kDa), confirmed its safety [33]. Studies on rats fed for 90 days with food enriched with 3% and 10% bovine colostrum also confirmed the safety of the colostrum, as no biochemical, physical, or histopathological abnormalities were observed in rats [34]. It is worth mentioning that before conducting this eight-week study on volunteers, the potential sensitizing and irritating effects of our cream with 15% sheep colostrum were tested on a group of 25 people. The results of this study showed that the cosmetic preparation did not cause any side effects in dermatological tests. Side effects of topical use colostrum can be the result of an allergy to colostrum components. Anaphylaxis after a cream with bovine colostrum was described [35], but what is worth noticing is that sheep milk is characterized by a lower content of frequent allergens [3; 36].