Contact dermatitis: etiologies of the allergic and irritant type Andris Rubins 1 ✉ , Anna Romanova 1 , Marcis Septe 1 , Spandana Maddukuri 2 , Robert A. Schwartz 2 , Silvestrs Rubins 1 ¹Department of Dermatovenerology, Faculty of Medicine, University of Latvia, Riga, Latvia. 2 Department of Dermatology, Rutgers New Jersey Medical School, Rutgers University, Newark, NJ, USA. 181 2020;29:181-184 doi: 10.15570/actaapa.2020.37 Introduction The term contact dermatitis describes an inflammatory process of the skin that occurs in response to contact with exogenous sub- stances and involves pruritic and erythematous patches. Contact dermatitis can occur in any region of the body; however, the face, hands, and neck are most commonly involved (1). The clinical manifestations of contact dermatitis depend on the exogenous substance, which is classified as either an allergen or an irritant, and the duration of exposure. Allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD), the two subtypes of contact dermatitis, are classified according to the causative agent. ACD is a delayed Type IV hypersensitivity reaction to exogenous contact antigens that the person has previously been sensitized to, where- as ICD is a nonspecific inflammatory response to direct chemical damage to the skin (Fig. 1) (2). The two subtypes of contact derma- titis are oſten present simultaneously (Fig. 2) (3). Epidemiology Approximately 80% of all contact dermatitis is ICD, whereas ACD makes up only 20% of contact dermatitis cases. According to the National Health and Nutrition Examination Survey (NHANES), the estimated prevalence of contact dermatitis in the United States is 1.4%. A similar prevalence rate of 1.2% was found specifically for ACD in a Dutch study (4). The incidence of occupational contact dermatitis can vary from nine to 49 cases per 100,000 workers per year (5). Correlations have been observed between the prevalence of contact dermatitis and both age and sex. The implications of age on the prevalence of contact dermatitis involve the differential ex- posure to allergens and irritants experienced by children versus adults. Common causes of ACD in children include, but are not Abstract The term contact dermatitis describes an inflammatory process of the skin that occurs in response to contact with exogenous sub- stances and involves pruritic and erythematous patches. Approximately 80% of all contact dermatitis is primary irritant contact dermatitis (ICD), whereas allergic contact dermatitis (ACD) makes up only 20% of contact dermatitis cases, the estimated preva- lence of contact dermatitis in the United States being 1.4%. Among patch-tested patients, nickel has been identified as the most common allergen. Cobalt is the second most common metal allergen and is found in various dental alloys, paints, and coloring components of porcelain and glass. The average prevalence of dermatitis due to p-phenylenediamine (PPD) was found to be 4.3% in Asia, 4.0% in Europe, and 6.2% in North America. Rubber gloves are a major cause of occupational ACD in healthcare workers. Occupations involving frequent handwashing, between 20 and 40 times per day, have shown an increased incidence in cumula- tive ICD. The prevalence of occupational hand dermatitis was 69.7% in workers that reported a handwashing frequency exceeding 35 times per shiſt. The use of alcohol-based sanitizers is much more prevalent among today’s healthcare workers than frequent handwashing. Both allergic and ICD are worldwide problems. Keywords: contact dermatitis, epidemiology, pathogenesis, treatment Acta Dermatovenerologica Alpina, Pannonica et Adriatica Acta Dermatovenerol APA Received: 18 March 2020 | Returned for modification: 30 June 2020 | Accepted: 20 August 2020 ✉ Corresponding author: arubins@apollo.lv Figure 1 | Allergic contact dermatitis (38). Figure 2 | Patch testing with 30 standard haptens.