## 4 Discussion
It should be noted that plant substances contain a wide range of active substances that may have the ability to change the color of a cosmetic product [44]. Among others, [PERSON] et al. [55] in their work analyzing the color assessment of cosmetic emulsions with plant extracts, i.e., globe amaranth (_Gomplrena globosa_ L.), butterfly pea (_Clitoria terntaea_ L.), safflower (_Carthamus tinctorius_ L.), pomegranate (_Punica sekretum_ L.), and corn poppy (_Papaver rheos_ L.), observed a change in the color of the emulsion from white (base sample) into yellow, red and blue-violet. It can, therefore, be concluded that natural raw materials do not always have a positive effect, acceptable to the consumer, on the color of the final product, which may change during storage. Skin hydration is an essential requirement for modern cosmetics, including cosmetic oils. The efficiency of the epidermal barrier depends on a properly developed stratum corneum [56]. It is composed of keratinocytes connected by a lipid matrix consisting of ceramides, cholesterol esters, and fatty acids. There is a hydrolipid coat on the surface of the stratum corneum. The weakening of this barrier may be caused by bacteria, allergens, diseases, and, consequently, inflammation. Rebuilding the proper protective barrier of the skin can be achieved by using emollients [57; 58; 59]. Taking into account the results obtained in this study, it can be concluded that the use of both synthetic and natural emollients in cosmetic oils contributes to the increase in skin hydration and lubrication. The greatestdifferences in skin hydration values before and after 2 h after applying the oils were recorded for the F2 recipe with a high proportion of Ricinus Communis Seed Oil (50%). This is due to the presence of fatty acids in the recipe, which have various effects on the skin. Formulation F2 contains castor oil, which belongs to the group of fatty emollients that are quickly absorbed by the skin. It is rich in ricinoleic acid (74-85%), linoleic acid (7.3-10.32%), and oleic acid (5.55-7.55%) (Table 2). Additionally, this formulation contains macadamia oil, in which oleic acid is present at a concentration of 54-68%. Ricinoleic acid, with its many derivatives, exerts skin-smoothing and moisturizing activities and recovers rough skin [60]. Oleic acid activates lipid metabolism, restoring the barrier function of the epidermis and retaining moisture in the skin [61]. Linoleic acid, the most abundant fatty acid in the epidermis, and its derivatives have an essential role in the structure and function of the SC permeability barrier. Linoleic acid, therefore, improves the epidermal barrier, protects against transepidermal water loss, and normalizes skin metabolism. Linoleic acid is also a natural component of sebun [62; 63]. Improving skin hydration through the use of embollient mixtures (from the group Isostearyl Isostearate, Propylene Glycol Dicaprylate/Dicaprate, PPG-3 Benzyl Ether Ethylhexanoate, PPG-3 Benzyl Ether Myristate, Triethylhexanoin, and Caprylic/Capric Triglyceride) in prototypes of olive-oil recipes for children in relation to olive oil containing only mineral oil was also demonstrated in work [64]. However, in the work published by [PERSON] et al. [65], the authors examined the effect of various vegetable oils from the steppe zone of Southern Ukraine (_Hypericum perforatum_ L., _Silbum maranium_ L., [PERSON], _Linum usitatsisimum_ L., _Tritcium aestivum_ L., _Sesamum indicum_ L., _Sinapis alba_ L., and _Cucirbita p e po_ L.) among others to moisturize and lubricate the skin. They found that the emulsion based on the proposed mixture of vegetable oils provided a good balance of moisture and fat on the skin for one hour, in contrast to the short-term effect of the emulsion based on mineral oil. The level of skin lubrication after application of the developed cosmetic body-oil formulations remained at a higher level in the case of formulations with a predominance of vegetable oils.