Good occupational disease statistics exist in few countries. The coverage differs greatly depending on the notification system, legal concept of occupational disease, and workers’ compensation coverage of different occupational groups. For example, farmers and other independent entrepreneurs are often missing from the statistics because they are not covered by compensation systems. Some statistics include only those that have lost work days for the skin disease. All statistics underestimate the true incidence of occupational skin diseases.

In epidemiological studies, the reported point prevalence of occupational hand dermatitis has been at least 10 % of workers in occupations with skin contact with allergens or irritants. This figure is much higher in risk occupations (examples: hairdressers, dental health workers, other health care workers, veterinarians). The majority of occupational skin diseases are contact dermatitis, either allergic or irritant, affecting mainly hands or forearms but also other (open) skin areas, mainly face. New sources of allergic contact or protein contact dermatitis are constantly found. Detection of the cause is crucial and the only way to attempt to cure occupational contact dermatitis.

According to the US Bureau of Labour Statistics, the incidence of occupational skin disease has decreased since 1994, and the same tendency can also bee seen in other countries (e.g. Finland). In the same statistics, the highest annual incidence of occupational skin disease has been in agriculture, forestry and fishing (in 1999 15,5/10 000) followed by manufacturing (11/10 000). Finnish Register of Occupational Diseases (FROD) has collected information on diagnosed cases of work-related diseases since 1964. Information is not based on compensation only but on notification by the physician diagnosing the disease. As of now, FROD has collected information on over 30,000 cases of occupational skin diseases. The register includes, on top of the diagnosis, causative agent(s), occupation, industry, age, and sex of the patient. Skin diseases are categorized into five diagnostic groups – allergic contact dermatitis (ACD), irritant contact dermatitis (ICD), contact urticaria or protein contact dermatitis (PCU), skin infections, and other. About 30-35% of occupational dermatoses have been ACD, about the same amount ICD, 15-20% PCU and 10-15% other skin diseases. The annual incidence has been about 4 cases/10 000 workers on average, 20/10 000 in food industry, 15/10 000 in farming and 12/10 000 in manufacturing. In the UK statistics which cover only a region of the country and dermatological patients that have been disabled for two weeks for skin disease, the top occupational groups are manufacturing/mining, social/personal services, health and education, agriculture, and construction.

There are many limitations to getting information on exposure to specific chemicals: product labeling as well as material safety data sheets (MSDS) are often limited (only substances exceeding a certain concentration, no byproducts, metabolites, or contaminants) and the information may be lacking or false. Especially (meth)acrylate containing products regularly contain undeclared (meth)acrylate compounds. Inquiries to manufacturers may take time and lack (specific) information. Product data bases can be simple and quick, but information is often limited to the needs of the provider, and updating is often a problem. Therefore, chemical analyses are sometimes needed to analyze products for potential allergens.

Risk occupations for irritant dermatitis include those with moisture, detergents, dirt, and chemical exposure. The most important causes for ACD in Finland have been rubber chemicals, synthetic resins and plastics (epoxy resin systems, (meth)acrylates, phenolformaldehyde resins), metals, plants, and biocides. Protein contact dermatitis (PCD), often clinically indistinguishable from ACD, and contact urticaria (CU), both representing immediate allergy, are caused mostly by proteinaceous substances in nature, including latex, food stuffs, animal proteins and plant proteins. Diagnosis of occupational allergy requires usually skin testing not only with standard series but with specific series and patient (workplace) supplied materials. Depending on the industry, about one third of occupational skin allergy can be immediate (PCD, CU), and therefore, in addition to patch tests, skin prick tests and/or specific IgE-antibody determinations (e.g., RAST) are needed for diagnosing these conditions.

History of atopy (childhood eczema, flexural eczema, allergic respiratory symptoms) or other constitutional risk factors increase the risk for occupational hand eczema. History of metal dermatitis (nickel allergy), wool intolerance, itch when sweating, or generally dry and itchy skin, all are markers of sensitive skin and predispose to irritant (and allergic) hand eczema. Pollen allergies often coexist with allergies to raw vegetables, fruits, and spices causing hand eczema (protein contact dermatitis) in, e.g., food handling. Atopic allergies seem to be major contributors to skin reactions in livestock farmers, veterinarians, and laboratory animal workers. Household work, renovation and maintenance of buildings, car maintenance, and some hobbies (exposure to paints, glues, garden, etc.) may also be major contributors to dermatitis.

Studies have shown that the prognosis of allergic dermatitis can be good once the allergen is detected and avoidance or protective measures started. Total removal from exposure often brings about rapid resolution, but it may take months if exposure and/or the reaction has been severe. In an uncomplicated case, the rash may resolve in 3-7 days but the skin will remain in a vulnerable state for at least 3 weeks. The prognosis is much worse if hidden exposure sources or other concomitant allergies (e.g., to corticosteroids), either at work or home, have not been detected and eliminated.