Work-related skin diseases

Introduction

Occupational skin diseases are among the top three registered occupational diseases in Europe ^[1]. Exposure to chemical, physical, biological risk factors can lead to different skin diseases, though several individual (genetic) factors influence the outcome too. The majority is caused by wet work, workplace exposure to chemicals and high ultraviolet radiation from the sun. Contact dermatites are the most prevalent and they may pose a serious threat to the work ability of the individual ^[2]. The prevention of occupational skin diseases requires a comprehensive approach with coordinated activities of the dermatologist, the occupational physician, the occupational hygienist and the occupational safety and health expert.

Definition of occupational skin disease

Occupational skin diseases (also known as occupational dermatoses) are skin diseases caused by exposures to hazards at work ^{[3] [4]}. In relation to skin the most relevant chemical hazards are irritants, sensitising, photosensitising and acnegenic agents. Biological hazards range from bacteria, fungi, viruses, to skin parasites. Physical hazards include rubbing, mechanical pressure, radiations and temperature. Epidemiology data does not represent the real extent of the issue, because most of the cases are not reported and the registration criteria vary from country to country ^[2]. It is estimated that 20-30% of occupational diseases are skin diseases, placing them among the three most frequent groups of occupational diseases ^{[1] [1]}. The most common cause of skin disease in the workplace is exposure to chemical substances. Non-melanoma skin cancer caused by UV rays is, however, an occupational hazard for outdoor workers, but as the disease is not recognised in most EU countries, its prevalence is greatly underestimated^[5]. As with any occupational disease, a certain degree of causal relationship between the skin disease and the occupation must be verified during investigation. Accordingly, there are two requisites: (i) making the right and specific medical diagnosis and (ii) verifying that the skin disease is related to the occupation ^[1]. For the latter, it is essential to be familiar with the work activity, the hazards at work, the occupational safety and health instructions and skin protection programme at the workplace. The European schedule of occupational diseases and the ILO list of occupational diseases both dedicate a section to occupational skin diseases ^{[6] [7]}.

Skin diseases of chemical origin

Exposure to chemical substances is a leading cause of occupational skin diseases ^{[1] [8]}. It is obvious because the worker’s first line of contact with its environment, aside from the respiratory tract, is the skin. As most work involves manual activities, the skin of the hands is very likely to be involved. The gloves and clothes should be checked for their adequacy to prevent exposure, as exposure may be a source of non-dermatological occupational diseases as well. Airborne exposure may require further prevention measures, like ventilation, special protective masks and goggles.

Contact dermatitis

The most common occupational skin disease, covering around 50-80% of cases, is irritant contact dermatitis, which is around five times more frequent than allergic contact dermatitis ^[8]. It is the inflammation of the skin at the place of contact with the chemical substance. Irritant contact dermatitis and allergic contact dermatitis are indistinguishable from each other by clinical or histological examinations. Furthermore, mixed form (allergic plus irritant) contact dermatitis is also very frequent. On one hand, a substance may have both irritant and sensitising properties; in addition, the worker may be exposed to multiple substances. On the other hand, irritant exposure harms the barrier function of the skin, which promotes sensitisation by enabling increased absorption of allergens ^{[9] [10]}. Previous or present atopic dermatitis is a strong risk factor for developing occupational contact dermatitis ^{[2] [11]}. Atopic dermatitis is a common skin disorder that is based on genetic disposition of decreased barrier function and impaired repair, and features itching and dryness ^{[12] [13]}. There is an abundant range of occupations and sectors that are at risk of occupational contact dermatitis including: hairdressers and beauticians, health care, construction, horticulture, textile industry, catering and food industry, rubber manufacturing, metalworking, electroplating and tanning ^{[2][8] [14] [15]}.

Irritant contact dermatitis (ICD)

Exposure to irritant chemical substances can directly damage the skin at the place of contact and lead to ICD. Common chemical agents include acids, alkalies, organic solvents and detergents. The effect on the skin depends not only on the chemical properties and the intensity of contact, but the concentration of the chemical as well ^[10]. Wet work is the leading cause of ICD ^[4]. The term refers to occupational activities that require: (i) the skin of one or both hands to be in contact with water or aqueous solutions irritants; or (ii) the sustained wear of protective gloves that makes the hands moist from perspiration ^[16]. Furthermore, such soakings disrupt the natural barrier in the skin and promotes the entry of sensitising agents; thus predisposing to the development of skin allergies as well ^[10]. Symptoms of ICD range from dryness, burning red rashes (erythema) and swelling (oedema) to the development of bullas (blistering), necrosis and peeling (desquamation) in more severe cases. Chronic, repeated exposures trigger the development of fully-fledged eczema: itching, cracking, crusting and flaking, oozing or even bleeding that may be present alongside the signs mentioned earlier ^[10][17]. Patch tests are negative in ICD that has no allergic component. However, in ICD the penetration of allergens through the skin is increased, which increases the risk of developing allergy. Among atopic individuals the skin has a lower capacity to resist against irritants, thus a short exposure to low doses may trigger the symptoms of inflammation ^[11].

Skin inflammation due to the combined exposure of a chemical substance and light (phototoxic dermatitis) can lead to developing vesicles and bullas (blistering) on the inflamed skin, which is followed by a characteristic skin tan (hyperpigmentation). The most frequent chemicals involved in phototoxic dermatitis are:

• Furocoumarins (psoralens) in plants ,which may make, for example, gardeners, florist and manufacturer of cosmetic particularly vulnerable ;
• tar derivatives, which may make, for example, road construction and building insulation workers particularly vulnerable;
• and pharmaceuticals, to which exposure may be present in certain pharmaceutical plants^[8][14][17]

Allergic contact dermatitis (ACD)

This form of skin inflammation may be acquired only after contact with a sensitising chemical substance. In ACD the sensitisation process can take weeks, months or even years and there is no allergic reaction to be seen on the skin during that period ^[8]. The hypersensitivity to the given chemical will practically last for life, although avoiding further contact with the chemical agent may lower the level of reaction. This allergy is a late onset cell-mediated immune response to the chemical substance, which explains why its symptoms have a latency period of days, which is longer than that of contact urticaria. Clinical signs of ACD are very similar to that of ICD, although itching is predominant over burning, furthermore skin lesions are not limited to the contact site but might develop at unexposed parts too. The most important occupational allergens are ^{[8][10] [14][18][15]}:

• metals - chromium, nickel, cobalt, mercury
• p-phenylenediamine (PPD)
• rubber additives
• natural resins
• artificial resins
• biocides
• preservatives
• animal feeds
• plants
• pharmaceuticals

A special form of ACD is photoallergic contact dermatitis. Here the chemical compound transforms into a complete sensitising agent only when exposed to ultraviolet light (mainly from the A-band spectrum). Fragrances (e.g., in cleaning, chemical industry), optical brighteners (e.g., in laundries, washing powder manufacturing), dyes (e.g., in textile industry), and pharmaceuticals are the most common chemicals involved in photoallergic contact dermatitis ^[8][14].

Airborne contact dermatitis (ABCD)

ABCD is characterised by a skin inflammation that is even and is primarily located on the face, around the eyes and neck. However, it may be present on the hands or even cloth-covered areas. This is caused by environmental dust (wood dust, textile fibres, cement, sand, glass fibre) or other chemical compound in the air (epoxy resins, acrylates, vegetable dust e.g. from the Compositae/Asteraceae family, pollens, propolis). The underlying pathology of ABCD can be either ICD or ACD, with the latter often being occupational in nature. The importance of ABCD is that it needs to be distinguished from photosensitivity, which can occur in the same parts of the body with the same localisation ^[14].

Contact urticaria (CU)

The symptoms of CU are itching and hives (urticaria). In immunologic CU the reaction is an immunglobulin E mediated early immunoresponse against the sensitising chemical substance. Thus in contact urticaria the chemical compound causes hives at the place of contact, usually within an hour ^[14]. This can be accompanied by (allergic) rhinitis, conjunctivitis, asthma and rarely anaphylaxis. There is also a non-allergic route (non-immunologic CU), where the chemical directly triggers histamine release in the skin causing urticaria ^[14]. Common sources of allergic CU are proteins (latex, fish, meats, eggs), plants (crops and ornamental plants, wood), bisphenol-A, chromium and cobalt. A well-known form of allergic CU is latex-allergy among healthcare, catering and cleaning workers who are wearing latex gloves. Direct CU can be caused by stinging-nettle, preservatives, additives, dyes, fruits, vegetables, cobalt, balsam of Peru ^{[14] [17] [18]}. Tackling CU is more difficult, because it requires a total elimination of the allergen due to the risk of the more serious complications; thus change of job is more frequently recommended to avoid/ prevent exposure^[17].

Diagnosis of contact dermatitis

Verifying chemical allergy is usually done by (epicutaneuos) patch testing, when minute dose of diluted substances are applied to the skin and observed periodically. If an occupational origin is suspected the general battery (baseline series), which contains everyday sensitising agents, should be supplemented by occupational series (common sensitising substances of a given sector/occupation) and/or substances used at work (based on the safety data sheets) ^[10]. There are further diagnostic tests available: patch test with early examination, photo patch test, use test, prick test, intracutaneous test. In vitro laboratory assays (e.g. quantitative IgE blood test) are less sensitive and specific. Tests identifying responsible immune cells are under research ^[8][10].

Occupational acne

These are comedos (pinheads), papules and pustules caused mostly by industrial oils and greases ^[14]. Unlike common acne, these eruptions manifest at the site of skin contact. Tar derivatives and halogen-containing compounds (polychlorinated naphtalenes, polychlorinated phenoxy phenols, 3 4-dichloroaniline and similar herbicides, iodides and bromides) may cause acne, just like certain pharmaceuticals. Car mechanics, maintenance workers are most at risk. Personal and work hygiene is of utmost importance in the prevention of oil acne. Frequent change and centralised washing of dirty work wear is necessary ^[8][14][17].

Skin cancers due to chemical exposure

Pitch, tar, soot, anthracene and compounds thereof, mineral and other oils, raw parafin, carbazole and compounds thereof, coal tar distillation products may cause a disturbance in the epidermis ^[19]. This can trigger the development of basal cell and squamous cell carcinomas, or conditions (keratotic papilloma, keratoacanthoma) that may lead to these cancers. Arsenic causes brownish pigmentation and rough, scaly patches (keratosis). Bowen's disease, squamous cell carcinoma and multiple basalioma may develop ^[8][14].

Prevention of skin diseases due to chemical exposure

Proper workplace skin protection programmes adapted to the actual situation are the best way to prevent occupational skin disease ^[20]. A thorough risk assessment is the basis for preventing harm and protecting the health of employees. Information on the chemical properties, risks and preventive measures are available on the label and in the Safety Data Sheets (SDS) of chemicals. In addition, Occupational exposure limits (OELs) also provide a basis for determining whether or not exposure levels in the workplace are harmful. OELs are regulatory values which indicate levels of exposure that are considered to be safe (health based)^[21]. However, OELS express the levels in terms of concentrations in the air. Therefore, for substances for which dermal absorption is important, the skin notation should be considered. The Scientific Committee on Occupational Exposure Limits (SCOEL) issues a skin notation indicating a possible significant uptake through the skin. A skin notation alerts risk assessors and occupational hygienists in the interpretation of workplace air monitoring results that may not reflect the total uptake of the substance if skin contact occurs due to workplace practices or usage. Usually, SCOEL issues a skin notation when it can be assumed that dermal exposure may contribute to about 10 % or more of the body burden by inhalation exposure at the occupational exposure limit^[22].

The prevention measures follow the hierarchy of control like in other occupational safety and health programmes. The initial target is to eliminate/minimise skin contact with harmful (carcinogen, irritant and sensitising) material and wet work ^{[8] [23]}. Personal protective equipment, gloves should be chosen according to the (chemical) properties of the risk, taking into consideration the tasks, the work environment and the worker. In order to minimise wet work, the duration of uninterrupted wearing of gloves should be minimised as well ^[24]. National initiatives and sectoral guides may provide useful information for the implementation of a skin protection plan. However, it must be always tailored to the actual situation of the given workplace. There are several examples of successful implementation of workplace skin protection plans. Information and training of workers on exposures, prevention techniques, proper use of personal protective equipment and skin hygiene is of fundamental importance ^{[25] [26]}. Health surveillance is recommended in order to identify the shortcomings of measures and workers that need advanced protection ^[27]. Support to the individual in maintaining healthy skin includes the provision of proper skin cleaning agents and skin rehydration products at the workplace ^{[28] [16] [28] [18] [14]}.

Infectious skin disease

Several infectious agents may be contracted from various sources during work, including animals at work (occupational zoonoses). The diagnostic and treatment process is identical to non-occupational diseases. Diagnosis is based on the clinical signs plus history and if required on laboratory blood tests, microscopy and growing cultures. Prevention is based on the risk assessment of the given workplace that takes into account unintentional exposure to biological agents. The measures follow the hierarchy of control and include proper personal and work hygiene, the use of germicide agents and gloves. In case of zoonoses the co-operation with the veterinarian is essential ^{[14] [29]}.

Bacterial infections

Occupational pyodermas (folliculitis, furuncle, carbuncle, impetigo, ecthyma, paronychia, etc.) can be caused by the Streptococcus and Staphylococcus bacteria which generate pus. These infections are common among those working in dirty environments (e.g., car mechanics, sewerage cleaners) where microtrauma (bruises, cuts) of the skin are common (e.g., butchers, slaughterhouse workers, machining of metals), or who may be in contact with infected persons (e.g., nurses, hairdressers, manicurists) ^[14]. Colonisation, which is the presence of microorganisms on the worker without apparent disease, and manifest infection with antibiotic resistant bacteria (e.g., MRSA) among health care workers is an emerging issue with implications for patient safety ^[30].

Erysipeloid is caused by Erysipelothrix rhusiopathiae. The infection presents in the form of marked skin inflammation that accompanies the inflammation of the underlying connective tissue (cellulitis). It is almost exclusively occupational, among butchers and workers in contact with fish and poultry ^[14].

Skin tuberculosis is a granulomatous, slowly progressing, wart-like skin lesion with regional lymph node involvement. Mycobacterium tuberculosis hominis may develop among pathologist, dissectors, and surgeons ^[14]. M. tuberculosis bovis might be an occupational skin disease of vets, animal handlers, butchers, farmers ^[29]. M. marinum infection is transmitted by fish and water in tanks or pools (fish tank granuloma) ^[31].

Erythema chronicum migrans (ECM), which is a ring-like slowly growing red rash, is the early sign of Lyme-disease (Borrelia burgdorferi infection). It is a common occupational skin disease among forestry and horticultural workers. If untreated, later phases might feature cutaneous lymphoid hyperplasia, which is a benign skin bump, and acrodermatitis chronica atrophicans, which is characterised by initial inflammation and swelling and later atrophy of the skin at the limbs ^[14][29].

Fungal infections (mycoses)

Yeast infections

The occupational infection, which is mainly caused by Candida albicans, occurs usually on the hands: onychomycosis (nail), paronychia (around the nail bed), interdigital mycosis (between the fingers or toes). Workers in canneries and confectioneries, and health care workers are at risk. Wearing rubber gloves and boots (wet work) and handling of sweets can be contributing factors to the development of these infections ^[14].

Dermatophyte infections (ringworm)

Trichophytia profunda is caused by Trichophytia verrucosum and looks like a deep bacterial skin infection. Farmers, milkers, animal handlers, and veterinarians may acquire it from infected cattle ^[14][29]. Microsporiasis is an infection of Microsporum canis that is common among pets (dogs, cats, guinea pigs) and may cause ringworm among pet traders and breeders, vets, laboratory workers. Microsporum gypseum lives in soil and may also infect agriculture workers ^[14].

Viral skin diseases

Milker's nodules (Nodus mulgentium) are caused by the Paravaccinia virus^[29]. The source is the udder of the cow, although less frequently the udder of sheep or goats, where it presents as a quickly healing wound. Milkers and other animal handlers may develop the skin lesion which heals spontaneously without scarring within weeks ^[14][29]. Orf (Ecthyma contagiosum) is caused by a Parapox virus, which is common in sheep and goats. The tender skin lesion may be accompanied by regional inflammation of the lymph vessels and nodes. The disease may be contracted by shepherds, goatherds, veterinarians and it may heal spontaneously without scarring within weeks unless the wound is superinfected ^[14][29].

Parasitic skin lesions

Although frequently unrecognised, parasitic skin diseases may have an occupational origin ^{[8] [32]}. Arthropod bites from animal parasites or granary mites are common in agricultural workers ^{[33] [34] [29]}. Bee and wasp stings are important, because their venom may cause serious and even life-threatening allergic complications. However, most beekeepers develop a kind of resistance where even a dozen bites may not cause any skin, or other effect ^[35]. Scabies is caused by Sarcoptes scabiei. This tiny mite digs itself into the skin around the wrists, elbows, hands, feet, back, buttocks, and external genitals causing itching and superficial burrows. The infection is transmitted by direct contact, e.g. during care activities. Treatment should involve contact persons without symptoms too^[36]. Control of infection is challenging for the health and social care institutions, which are most at risk ^[37].

Skin diseases of physical origin

Physical exposures range from direct stimuli and thermal conditions to radiation.

Mechanical trauma

Recurring rubbing or increased pressure can thicken the inflamed skin with “crazy-paving pattern" (lichenification) and callosity (ref). So-called occupational stigmas are frequent at body parts exposed: shoulders of sack carriers, fingertips of guitarist and violinists, knuckles of masseurs, hands of blacksmiths. The conditions are only of aesthetic nature and reversible; prevention is usually impossible ^[8].

Temperature

Besides their physiological effect on the human body, extreme temperatures can cause specific alterations in the skin ^[14]. They are on the border of diseases and accidents, however, due the time characteristics, the severe forms are rather considered accidents at work. The prevention is based on insulation, appropriate clothing and work organisation (rotation of workers and specified recovery areas for breaks and shelter).

Heat

Sweat stagnation can cause miliaria (~crystallina, rubra, profunda), which are small and itchy rashes (sweat rash, prickly heat). Overlapping skin surfaces can become sodden, ending up in intertrigo; which is an infectious inflammation of body folds. Heat and physical exercises may cause heat urticaria: non-allergic hives. Intense heat can cause burns. The metallurgy sector, bakeries, kitchens, summer outdoor jobs (agriculture, construction), and deep mining are typical exposures^[14].

Cold temperature

The effects of cold to the skin may range from progressive vasoconstriction (narrowing of blood vessels) and Raynaud-like symptoms (blanching attacks of fingers) to frostbites. Cold-storage and winter outdoor (e.g. maintenance, construction) jobs are examples for such exposure^[14].

Ionising radiation

Ionising radiation is used widely in medical imaging and therapy, industrial quality inspection, and the sterilisation of medicines and foods ^[38]. Occupational exposure to ionising radiation, including X-ray, usually causes local skin signs (radiation dermatitis). X-ray and gamma radiation can penetrate deeper, and thus, harm inner layers than beta radiation which is absorbed superficially, or even by the clothes ^[39]. As technology is improved and made safer due to consistent occupational safety and health standards, local radiation burns are very rare nowadays ^[40]. The skin symptoms after a short high level exposure to ionising radiation are termed acute radiodermatitis, while the effects of long term exposure is summarised as chronic radiodermatitis^[14]. Their prevention is mainly technical (enclosure of the technology, segregation, proper maintenance) accompanied by strict protocols, shielding devices and personal protective equipment.

Acute radiodermatitis

After a single dose of around 10 Grays or more, local redness (erythema), swelling (oedema) and loss of skin colour develops. Nausea and vomiting may be present. After days of latency the disease may progress with a painful livid inflammation with vesicles and bullas (blistering) and necrosis that heals with scar, atrophy and loss of hair ^[14].

Chronic radiodermatitis

Repeated exposure to smaller (3-8 Grays) doses with a total of 50-60 Grays causes atrophic indurated plaques, spider veins (telangiectasia) or even thickening (hyperkeratosis), a syndrome called termed poikiloderma. Skin cancer can arise after months or years on the grounds of poikiloderma ^[14].

Non-ionising radiation

Concerning occupational skin diseases, workplace exposure to ultraviolet radiation is among the most important physical risk factors ^[8]. Although ultraviolet radiation is necessary for the human body to produce vitamin D, excessive exposure is harmful: it damages the skin and the eyes, causes mutation of the DNA and suppresses normal immunologic responses ^[41]. Clinical signs depend on the magnitude and the actual wavelength of exposure and, to a lesser extent, on individual factors: e.g. darker skin can provide some protection against sunburn. Acute effects of ultraviolet radiation ranges from skin tan, red rash (erythema) to the various levels of sunburn. Chronic exposure can cause increased pigmentation, premature aging of the skin (photoaging), development of rough, scaly patches (solar keratosis) and squamous cell cancer, and less frequently basal cell carcinoma (basalioma). Skin cancers may be preceded by keratosis and keratoacanthoma ^[14]. Subjects of ultraviolet radiation are outdoor workers and those exposed to artificial ultraviolet radiation (welding, UV lamps and lasers used in medicine, industry, trade and at home). Prevention of occupational skin cancers due to radiation consists of proper occupational safety and health organisation and instructions, shields, hats and (UV-absorbent) clothing together with medical surveillance. During medical check-ups keratoses can be discovered for treatment, while workers with verified skin cancers should be removed from exposure ^{[8][17][14][42]}.

Conclusions

Occupational skin diseases are common and have significant effects on the life of the workers concerned. The number of affected workers is expected to rise as the number of chemicals used is increasing and disposition to develop an allergic reaction is getting more and more common. Identification of disorders can be easily done by medical inspection during health surveillance. With appropriate measures most diseases can be cured, however, when elimination of exposure appears impossible, change of profession might be necessary in the end.