Hand dermatitis, also known as hand eczema, is common and affects a considerable number of individuals across all ages. The impact of hand dermatitis can be profound, as it can impair one’s ability to perform tasks at home and at work. As a result of the coronavirus disease 2019 (COVID-19) pandemic, there has been an increased focus on hand hygiene and subsequently hand dermatitis. There are many contributors to the severity of hand dermatitis, including genetic factors, immune reactions, and skin barrier disruption. In this column, we will explore irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD) of the hands, including epidemiology, potential causes, clinical characteristics, diagnosis, and management.
Epidemiology
The prevalence of hand dermatitis in the general population is 3% to 4%, with a 1‐year prevalence of 10% and a lifetime prevalence of 15%.1 In a Swedish study of patients self-reporting hand eczema, contact dermatitis comprised 57% of the total cases (N=1385); ICD accounted for 35% of cases followed by ACD in 22%.2 A recent study on hand dermatitis in North American specialty patch test clinics documented that the hands were the primary site of involvement in 24.2% of patients undergoing patch testing (N=37,113).3
The hands are particularly at risk for occupation-related contact dermatitis and are the primary site of involvement in 80% of cases, followed by the wrists and forearms.4 Occupations at greatest risk include cleaning, construction, metalworking, hairdressing, health care, housework, and mechanics.5 Even prior to the COVID-19 pandemic, occupational hand dermatitis was common; in a survey of inpatient nurses, the prevalence was 55% (N=167).6 More recently, a study from China demonstrated a 74.5% prevalence of hand dermatitis in frontline health care workers involved in COVID-19 patient care.7
Etiology of Hand ICD
The pathogenesis of ICD is multifactorial; although traditionally thought to be nonimmunologic, evidence has shown that it involves skin barrier disruption, infiltration by immunocompetent cells, and induction of inflammatory signal molecules. The degree of irritancy is related to the concentration, contact duration, and properties of the irritant. Irritant reactions can be acute, such as those following a single chemical exposure that results in a localized dermatitis, or chronic, such as after repetitive cumulative exposure to mild irritants such as soaps.
Hand hygiene products (eg, soaps, hand sanitizers) can be irritants and have recently gained notoriety given their increased use to prevent COVID-19 transmission.8,9 Specific irritants include iodophors, antimicrobial soaps (chlorhexidine gluconate, chloroxylenol, triclosan), surfactants, and detergents. Wolfe et al10 showed that detergent-based hand cleansing products had the highest association with ICD, which was thought to be due to their propensity to remove protective lipids and reduce moisture content in the stratum corneum. Although hand sanitizers are better tolerated than detergents, they can still contribute to ICD by stripping precious lipids and disrupting the skin barrier.11 Compared to ethanol, isopropanol and N-propanol cause more disruption of the stratum corneum.12 In addition, N-propanol has the same irritant potential as the detergent sodium lauryl sulfate.13 Thus, ethanol-based sanitizers may be better tolerated. Disinfectant surface wipes may include the irritant N-alkyl dimethyl benzyl ammonium chloride. Conversely, hand and baby wipes are formulated specifically for the skin and may be less irritating.11
Occupational contributors to hand ICD include chemical exposures and frequent handwashing. Wet work, mechanical trauma, warm dry air, and prolonged use of occlusive gloves also are well-known irritants.4 Fine or coarse particles encountered in some occupations or hobbies (eg, sand, sawdust, metal filings, plastic) can cause mechanical irritation. Exposure to physical friction from repeated handling of metal components, paper, cardboard, fabric, or steering wheels also has been implicated in hand ICD. Other common categories of occupational irritants include hydrocarbons, such as oils and petroleum.5,14
In addition to environmental factors, atopic dermatitis is an important endogenous factor that increases the risk of ICD due to underlying deficiencies within the main lipid15 and structural16 barrier components. These deficiencies ultimately lead to a lower threshold for the activation of inflammation via water loss and a weakened barrier. Studies have demonstrated that atopic dermatitis increases the risk for developing hand ICD 2- to 4-fold.17