Contact Allergy to Preservatives

Abstract

Every water-containing product needs preservatives to prevent microbial contamination in order to ensure product stability and consumer safety. These preservative agents can be natural or, more often, synthetic in nature. Beside displaying direct antimicrobial effects, some of them also function as antioxidants and/or have additional properties (“polyfunctional ingredients”). As their mode of action often implies interaction with microbial proteins, human skin proteins may become a target as well, leading to skin sensitization (contact allergy) and subsequent allergic contact dermatitis; other clinical manifestations such as contact urticaria, mucosal symptoms, and respiratory complaints may also occur, or coexist. Sensitization rates, and their evolution over time, may vary depending on the inherent sensitization potential of each chemical, their extent of use, legislative restrictions, and the type of population(s) involved (e.g., consumers vs. occupations). In this chapter, we give an overview of commonly used (cosmetic) preservatives, notably those present in the European baseline series and recommended additions 2019, including formaldehyde and releasers, isothiazolinones, parabens, methyldibromo glutaronitrile, and sulfites. Additionally, some less well-known preservatives are discussed, some of which might be potentially emerging sensitizers, such as benzoic and sorbic acid, and their salts (sodium benzoate and potassium sorbate, respectively), ethylhexylglycerin, iodopropynyl butylcarbamate, chlorhexidine digluconate and diacetate, polyhexamethylene and polyaminopropyl biguanide, benzalkonium chloride and didecyldimethylammonium chloride, triclosan, chlorocresol, chloroxylenol, phenoxyethanol, and (dichloro)benzyl alcohol.