## 1 Introduction
Products based on natural and safe ingredients are gaining popularity, and consumers are looking for cosmetics with minimal formulations that are still effective [4]. The use of eugenol and isoeugenol can not only meet the functional requirements related to extending the shelf life of products but also address the needs of conscious consumers looking for cosmetics that are highly effective with minimal risk of irritation [5; 6]. Research demonstrates that eugenol is effective against a wide range of microorganisms, including Gram-positive bacteria such as _Staphylococcus aureus_ and _Enterococcus faecalis_, with the minimum inhibitory concentrations (MICs) in the range of 0.5-2.0 \(\upmu\)g/mL depending on the strain and the testing conditions [6; 7; 8]. The action of eugenol against _Bacillus subtilis_ and _Bacillus cereus_, pathogens responsible for food poisoning, was also confirmed; for _B. subtilis_, the MIC was 0.1 mg/mL, and the minimum bactericidal concentration (MBC) was 0.3 mg/mL [9; 10]. Eugenol also inhibits _Bacillus anthracis_, the causative agent of anthrax, with the MIC ranging from 4 to 8 \(\upmu\)g/mL, suggesting its potential therapeutic applications [11]. Against foodborne pathogens such as _Listeria monocytogenes_ and _Listeria Ivanovii_, eugenol exhibits strong antibacterial activity--with MIC values of 1-4 \(\upmu\)g/mL--and microscopic analyses confirm damage to the cell membranes, leading to aggregation and cell death [12; 13]. In the case of bacteria such as _Clostridium difficile_, eugenol not only inhibits growth but also reduces toxin production, which may have applications in treating infections resistant to traditional methods [14]. Studies on the effectiveness of eugenol against Gram-negative bacteria, such as _Escherichia coli_, _Pseudomonas aeruginosa_, _Klebsiella pneumoniae_, and _Acinetobacter humantii_, show the MIC values ranging from 0.25 to 2.5 \(\upmu\)g/mL and MBC values from 1.0 to 5.0 \(\upmu\)g/mL, underscoring its versatility as the antibacterial agent [15; 16; 17; 18]. Eugenol's action against fungi, particularly _Candida albicans_ and other _Candida_ species, was confirmed in tests with MIC values ranging from 0.5 to 1.0 \(\upmu\)g/mL and MBC values from 2.0 to 3.0 \(\upmu\)g/mL [19; 20; 21]. Against _Aspergillus niger_, which poses a threat to immunocompetent individuals, the MIC was 1.0-2.0 \(\upmu\)g/mL [22]. Isoeugenol, a structural isomer of eugenol, exhibits similar antibacterial activity, including against the MRSA (_Methicillin-Resistant Staphylococcus aureus_) strains of _Staphylococcus aureus_, with MIC values of 0.25-1.0 \(\upmu\)g/mL [23; 24]. Its activity against Gram-negative bacteria, such as _Pseudomonas aeruginosa_ and _Escherichia coli_, remains in the MIC range of 0.5-2.0 \(\mu\)g/mL [25; 26; 27]. Isoeugenol's antifungal properties against _Candida_ show MIC values from 0.5 to 1.5 \(\mu\)g/mL, making it effective in treating fungal infections as well [28; 29; 30]. The ability of eugenol and isoeugenol to disrupt cell membrane integrity, disturb cellular homeostasis, and inhibit key enzymes makes them effective preservatives and antibacterial agents in cosmetics [31; 32; 33; 34; 35; 36; 37; 38; 39]. Cosmetic formulations are exposed to microbiological contamination, which is why they must meet specific microbiological cleanliness standards to ensure user safety. Microorganisms that can be found in cosmetics include bacteria, fungi, viruses, and yeasts. In cosmetics, only microorganisms that do not pose a health risk to consumers are allowed. For example, bacteria such as _Staphylococcus_, _Pseudomonas_, and _Enterococcus_ should be minimized, and their presence should not exceed the specified levels in the final product. Furthermore, fungi such as _Aspergillus_ and _Candida_ should also be controlled to prevent skin infections. Microbiological requirements include parameters such as total microorganism count, the presence of pathogenic bacteria, tests for fungi, and the product's shelf life.