Fig. 9.1
Insidious onset of irritant contact dermatitis in a 17-year-old hairdressing apprentice
Fig 9.2
Progressing irritant contact dermatitis in a 32-year-old construction worker, showing redness, infiltration, scaling, and fissuring
An acute irritant contact dermatitis has a variable clinical appearance often indistinguishable from an allergic eczema, while acute toxic reactions (chemical burns) resulting mostly from strong acids or alkalis usually present with a sharp demarcation and clinical signs of severe tissue damage, beginning with (sometimes bullous) edema and painful whitening and resulting in deep necrosis and scarring [7].
An acute allergic eczema usually presents 24–48 h after allergen contact with symptoms like redness, edema, vesiculation, and itching in the acute phase, while a chronic allergic contact eczema often resembles a chronic irritant dermatitis with scaling and fissuring. A spreading beyond the borders of the allergen contact can be frequently seen and may also affect other exposed body regions like the face and the forearms especially in airborne contact dermatitis. Frequent occupational allergens causing airborne contact dermatitis are epoxy resins, preserving agents like chloromethylisothiazolinone, or plant components like sesquiterpenlactones deriving from the plant family of Compositae, which may also cause an irritant dermatitis.
Atopic hand eczema is often characterized by vesicles in the palms or lateral fingers but may also affect the back of the hands, sometimes also presenting as nummular type. The volar wrist is often affected including the “tabatière.” Atopic individuals are also predisposed to develop hyperkeratotic fingertip eczema (“pulpitis sicca”). Atopic hand eczema flares are often not strictly work related but have their own dynamics.
In addition, a psoriasis vulgaris may sometimes be triggered by occupational factors like friction, heat, mechanical pressure, or occlusion (Koebner phenomenon). In this case, the psoriatic lesions are induced or aggravated in the skin regions affected by occupational irritant and mechanical or allergic influences and usually improve when the occupational “traumiterative factor” is reduced, e.g., by protection measures. The course of the disease should be at least in part work related (i.e., improvement during longer work-free periods) to make the diagnosis of an “occupationally induced psoriasis” [16]. Other differential diagnoses may include pustulosis palmoplantaris, mycosis, palmoplantar keratosis, lichen ruber or herpes simplex, and with regard to airborne contact dermatitis photoallergic/phototoxic reactions and seborrheic dermatitis.
9.4 Main Causes
Irritant factors play a causative role in up to 80 % of occupational skin diseases, primarily determined by “wet work,” including frequent contact of the skin with water, soap, detergents, or occlusive gloves. The German guidance TRGS 401 recommends that the duration of wet work (including use of occlusive gloves) should not exceed 2 h per work shift, and also, the frequency of handwashing or hand disinfection should be taken into account (especially when exceeding 20 times per work shift). Usually, several chemical irritants are involved and may cumulate together with mechanical, thermal, or climatic factors to low-grade damage within weeks or months. As a consequence, pH homeostasis is impaired allowing irritant factors like water or detergents to penetrate in the stratum corneum where they induce edema, decreased adhesion of corneocytes, and repetitive washing out of epidermal lipids, the latter constituting the “mortar” of the skin barrier. In addition, dust or dry dirt can induce or contribute to irritant contact dermatitis.
An atopic skin diathesis was significantly associated with hand eczema, and wet work ≥2 h/work shift was positively related to the presence of irritant hand eczema in a long-term follow-up study in the car industry [3]. In several studies, previous or current atopic dermatitis has been determined as significant risk factor for the development of occupational hand eczema in “wet work professions,” while in most of these studies, hay fever and/or bronchial asthma without atopic skin disease did not show a markedly increased risk of developing hand eczema [7]. Individuals with atopic dermatitis have often persisting dry skin for the rest of their life showing histological signs of subclinical eczema. Also, subjects without atopy may have dry or sensitive, hyperirritable skin due to a genetic predisposition for an impaired stratum corneum function, e.g., due to altered filaggrin [15] or cytokine expression. In some subjects, secondary (acquired) hyperirritability may persist for months or even years after the eczema has healed [14].
An allergic contact dermatitis often develops in a second step as a consequence of impaired barrier function induced primarily by chronic irritant dermatitis potentially allowing the repetitive penetration of substances acting as haptens (<500 kDa) in the dermis. In addition, persisting inflammation may facilitate the development of an allergic sensitization requiring both signals of innate and acquired immunity (see also the chapter about allergic contact dermatitis). Allergens may also directly stimulate factors of innate immunity which has been shown for nickel activating the expression of toll-like receptor 4 [18].
In contrast to a principally reversible chronic irritant dermatitis, an allergic sensitization persists throughout the whole life. Therefore, after patch testing, it is absolutely essential to assess the identified allergens for their true clinical and occupational relevance and take care of adequate prevention and avoidance strategies whenever possible. Also, cases should be notified as early as possible; there is no innocent irritant skin lesion in wet work occupations.
9.5 Risk Occupations
Table 9.1 summarizes a selection of professions where occupational skin diseases are frequent, including irritant and allergic factors typically present in the specific workplace.
Table 9.1
Selection of professions where occupational skin diseases are frequent, including main specific irritant and allergic workplace exposures
Occupation | Irritants | Allergic sensitizers (type IV/type I) |
|---|---|---|
Health occupations | Wet work (direct or occlusion), disinfectants, soaps and detergents, pestled pills | Type IV: glove ingredients, drugs (e.g., tetrazepam), disinfectants with aldehydes or quaternary ammonium compounds, fragrances in masseurs and geriatric nurses |
Type I: latex, formaldehyde | ||
Hairdressers | Wet work (direct or glove occlusion), dyes, shampoos, permanent wave liquids, bleaching agents | Type IV: oxidative dyes (para-aminoaryl derivatives), ammonium persulfate, preservatives, fragrances, perming substances (thioglycolate), glove ingredients |
Type I: latex, ammonium persulfate, p-phenylenediamine (rare) | ||
Florists, gardeners, plant growers | Irritant plants, fertilizers, pesticides, manure | Type IV: rubber materials, plant proteins (e.g., Compositae: main allergen sesquiterpenlactones) |
Type I: e.g., pollen proteins | ||
Plastic industry workers | Solvents, acids, ingredients in epoxy resins, oxidizing agents, acrylic monomers | Type IV: epoxy resins and hardeners, phthalates, acrylates, diisocyanates, formaldehyde |
Type I: diisocyanates, formaldehyde | ||
Painters and varnishers | Solvents, emulsion paints, paint removers, organic tin components, hand cleansers, glues, epoxy resins, glove occlusion | Type IV: epoxy resins, preservatives (isothiazolinones), thiurams, colophony, turpentine and substitutes, color pigments (chromate and cobalt) |
Construction industry (masons, floor layers, tilers) | Emulsion paints, wet work (direct or glove occlusion), wood preservatives, glue, cement, acids | Type IV: epoxy resins and hardeners, acrylates, diisocyanates, thiurams, chromate and cobalt |
Type I: diisocyanates (asthma) | ||
Metal workers, mechanics, galvanizers | Cooling system fluids, lubricants, detergents, solvents, cleaning solutions, degreasers, antifreeze, battery acid, wet work (direct or occlusion) | Type IV: ingredients of cooling system fluids (formaldehyde releasers or isothiazolinones), anticorrosives (e.g., monoethanolamine), fragrances (as additives), rubber materials, metals |
Food professions (bakers and pastry makers, cooks, catering industry, butchers) | Wet work (direct or glove occlusion), soaps, detergents, vegetable and fruit juices, spices, fish, meat, dressing, vinegar, enzymes, acetic, ascorbic, and lactic acid | Type IV: flavors, fragrances, spices, preservatives (e.g., benzoates), food colorants |
Type I: natural latex, proteins from fish, crustaceans, meat, flour, enzymes (also as protein contact dermatitis) | ||
Dentists and dental technicians | Wet work, soaps and detergents, soldering fluxes, adhesives, acrylic monomers, solvents | Type IV: dental metals, acrylic monomers, eugenol |
Type I: latex |
9.6 How to Make the Diagnosis
The relationship between clinical type of hand eczema and etiological diagnosis fits with general clinical experience (see main clinical features), but no simple relationship was found to make a clear diagnosis based on morphology and/or distribution alone. Irritant contact dermatitis often appears as chronic, dry fissured hand eczema (44.3 %), pulpitis (41.7 %), and nummular hand eczema (40.9 %) [13]. Furthermore, the lack of itching and slow aggravation after resuming work may be clues indicating chronic irritant dermatitis.
In allergic contact dermatitis, vesicular types with recurrent (35 %) and few (24.2 %) eruptions dominate which, however, are also typical for atopic hand eczema. A careful history of time-dependent development of lesions, patch testing, and exposure analysis is always mandatory to confirm allergic contact dermatitis. The localization may give a clue to an allergic sensitization (e.g., jeans’ button dermatitis and nickel sensitization or dermatitis demarcated along the “glove borders” in thiuram sensitization, Fig. 9.3).
