# Overview of Active Ingredients Used in Deodorants and Antiperspirants Available on EU Market
## 1 Introduction  
Although sweating is a natural physiological thermoregulatory function, it has the undesirable effect of an unpleasant body odour that causes discomfort. Therefore, deodorants are used to counteract the odour caused by the bacterial decomposition of skin secretions in the armpits, feet, and other areas of the body and to increase the pleasantness of skin odour. Antiperspirants, on the other hand, prevent sweating by blocking the sweat glands [1, 2]. Deodorants act on the effects of sweat secretion, but do not influence its composition or production. Depending on the active ingredients used, they work via different mechanisms. Deodorants work by inhibiting the growth of odour-causing bacteria, masking unpleasant odours, inhibiting the processes that lead to the formation of volatile compounds with an unpleasant odour, or by binding/absorbing such ingredients. Therefore, they act on the effects of sweat secretion, but do not influence its amount. Examples of deodorizing substancesinclude Carylyl Glycol, Alcohol, C12-15 Alkyl Benzoate, and Zinc Ricinoleate [2; 3; 4]. The effect of deodorants can be enhanced by lowering the pH of products using weak acids, such as Lactic acid and Citric Acid, and antioxidants, such as BHT and Tocpheryl Acetate [5]. Antiperspirants reduce sweat secretion by creating a barrier on the skin surface. When sweat is not released from the sweat glands, its components do not undergo bacterial decay and, consequently, no unpleasant odour is produced. Most use aluminium-based compounds, such as Aluminium Chlorohydrate (ACH), Aluminium Sesquichlorohydrate, Aluminium Zirconium Tetrachlorohydrorex Gly, and Potassium Alum, as active compounds. After an antiperspirant is applied to the underarm area, its component aluminium compounds polymerize under the influence of physiological pH, forming a gel which seals the openings of the sweat glands on the skin surface. This blockade is not permanent and disappears when the area is washed thoroughly with a cleanser, after very heavy sweating, or as a result of the keratinization process [2; 4; 6; 7]. The market for deodorants and antiperspirants is very extensive, and products are sold in a variety of forms and applicators; most are roll-ons, sticks, or aerosols, with others being sold as creams, gels, powders, and pastes. Some contain additional moisturizing, soothing and anti-inflammatory compounds, such as pantenol, allantoin, hyaluronic acid, aloe barbadensis leaf extract, saliva hispanica, and seed oil, which provide more comprehensive care for the skin [4]. Almost all forms of deodorants and antiperspirants contain fragrance compositions of natural or synthetic origin to mask unpleasant odours. Fragrance components derived from essential oils, e.g., limonene, linalool, citronello1, geraniol, and cinnamyl alcohol, exhibit a range of other biological properties desirable for deodorants and antiperspirants, including antibacterial, antifungal, and anti-inflammatory effects [8; 9]. In accordance with European Parliament and European Community (EC) Council Regulation No. 1223/2009, aluminium-zirconium chloride hydroxide complexes, Al\({}_{\text{x}}\)Zr(OH)\({}_{\text{y}}\)Cl\({}_{\text{z}}\), and aluminium zirconium chloride hydroxide glycine complexes may be used in \"ready-to-use\" antiperspirants at a maximum concentration of 20% as anhydrous aluminium zirconium chloride hydroxide or 5.4% as zirconium. Aluminium-zirconium compounds are also subject to the following restrictions: \"The ratio of the number of aluminium atoms to that of zirconium atoms must be between 2 and 10. The ratio of the number of (Al + Zr) atoms to that of chlorine atoms must be between 0.9 and 2.1\"; in addition, they should not be applied in aerosol dispensers or used on irritated or damaged skin [10]. There has been much controversy surrounding the safety of aluminium-based compounds in antiperspirants, which are alleged to cause breast cancer [11; 12] and neurodegenerative diseases [13; 14; 15].