98 JOURNAL OF COSMETIC SCIENCE “ethylhexylglycerin,” “methylparaben,” “ethylparaben,” “propylparaben,” “butylparaben,” “natural antimicrobial agents,” “phenoxyethanol,” “sorbic acid,” “potassium sorbate,” “mode of action,” “safety assessment,” “irritant contact dermatitis,” “natural antimicrobial agents,” “contact dermatitis,” and “antimicrobial resistance.” INCLUSION AND EXCLUSION CRITERIA Selection criteria included articles that examined antimicrobial ingredients antimicrobial preservatives the relationship between COVID-19 and personal care products and cosmetics market trends that directly impact cosmetic preservatives the mode of action of antimicrobial agents safety assessment of preservatives irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD) to preservatives and antimicrobial resistance to preservatives. Articles that evaluated only other cosmetic ingredients that were not included in this study were excluded. COSMETIC PRESERVATION The COVID-19 pandemic has enhanced personal hygiene habits with products focused on sanitization, and this new scenario is also impacting cosmetic products. A study to evaluate hygienic and cosmetic care habits in Polish women during the COVID-19 pandemic demonstrated a change in the frequency of handwashing before and during the pandemic. Noticeable increases in frequency compared to the time before the pandemic were recorded after using public transport (from 53.6% to 80.7%) and after coming back home (from 80.0% to 100.0%). Other results demonstrated that the frequencies of taking showers and the use of hand cream increased, the number of people who washed their face only once a day decreased, while for most people, the frequency of hair washing did not change. The frequency of using antibacterial products has increased however, excessive handwashing with detergents or disinfectants can damage the hydrolipid mantle of the skin surface and may also be responsible for irritation and even the development of contact dermatitis (CD) (3). Cosmetic products without preservation system rapidly become contaminated with molds, fungi, and bacteria, resulting in spoilage and increased infection risk. Particularly problematic microbes include the Gram-positive S aureus and the Gram-negative Escherichia coli (9). Even though preservatives are usually used in small concentrations, they are considered one of the main factors causing allergies in users (4). The number of cosmetic products available on the market continues to increase together with the rates of adverse cutaneous reactions. Approximately 6% of the population is sensitized to the ingredients of cosmetics, especially to preservatives and fragrances (10,11). The amount of antimicrobial agent to be used in a product depends on the agent’s intended role high concentrations are used for active substances in antimicrobial products (topical antimicrobials), and low concentrations are used for preservative purposes in cosmetic products (12), such as benzalkonium chloride (BAC) and chloroxylenol (CX). Currently, with the COVID-19 pandemic, antibacterial and antiviral agents have gained a fundamental role in personal care and cosmetic products. Until recently, we used a small amount of antimicrobial agent, while new products have emerged with these ingredients as leading features of the formulation. Table I describes the preservatives used in this study, as well as their modes of action and the maximum concentrations allowed.

Table I Modes of Action and Maximum Concentrations Allowed for Antimicrobial Preservatives Substance CAS number Mode of action Maximum concentration allowed a Other Reference Benzalkonium chloride (BAC) 8001-54-5 • Decreases surface tension • Inactivates enzymes • Degrades cell-proteins 0.1% Avoid contact with eyes (16–18) Benzoic acid (BEC) Sodium benzoate (SB) 65-85-0 532-32-1 • Acidifies the external environment, making it unfavorable to microbial growth • Inhibits enzymes from the cellular metabolism 2.5% (acid) – rinse-off products, except oral care 1.7% (acid) – oral care 0.5% (acid) – leave-on products (19,20) Benzyl alcohol (BA) 100-51-6 • Induces membrane lysis in bacteria • Denatures the structure of proteins by binding to amino acid residues 1% (12,21) Caprylyl glycol (CG) 1117-86-8 • Destabilizes and disrupts the microbial cell membrane and may inhibit DNA synthesis 0.5–1% Up to 5% (22,23) Chloroxylenol (CX) 88-04-0/ 1321-23-9 • Causes membrane damage, resulting in leakage of cytoplasmic constituents 0.5% (18,24) Chlorphenesin (CP) 104-29-0 • Denatures proteins • Inhibits protein synthesis 0.3% (12,25) Ethylhexylglycerin (EEG) 70445-33-9 • Disrupts membrane integrity • Affects the interfacial tension at the cell membranes of microorganisms 0.5–2% Up to 2% -sprayed products Up to 8% -maximum in rinse-off products (4,26–28) 99 PRESERVATION OF PERSONAL CARE AND COSMETIC PRODUCTS