Occupational Contact Dermatitis: Chefs and Food Handlers
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Chefs and food handlers are at high risk for developing occupational skin diseases.
Incidence rates per 10,000 workers per year range from 2.9 (butchers/food processing industries) and 6.6 (cooks) up to 23.9 (pastry cooks) and 33.2 (bakers). Irritant contact dermatitis is the most prevalent occupational disease in chefs and food handlers followed by allergic contact dermatitis (most frequently due to Compositae (foods), thiurams (gloves), and formaldehyde (detergents and disinfectants)). Food-handling occupations are also prone for IgE-mediated protein contact dermatitis and immunological (IgE-mediated) and nonimmunological occupational contact urticaria. Some foods and food additives can trigger several of these mechanisms independently and may induce different clinical pictures. The prerequisite for a successful treatment is the individual identification and exclusion of the disease-eliciting allergen(s) as well as implementation of skin protection.
KeywordsFood handler Butcher Cook Pastry cook Baker Chef Food processing Irritant contact dermatitis Allergic contact dermatitis Protein contact dermatitis Contact urticaria Allergen IgE Food additive
Chefs and food handlers are at high risk for developing occupational skin diseases. Individual incidence rates in different food handling occupations are discussed in Sect. 2 (Epidemiology and Risk factors) of this chapter.
Irritant contact dermatitis is the most prevalent occupational disease in chefs and food handlers followed by allergic contact dermatitis (most frequently due to compositae (foods), thiurams (gloves), and formaldehyde (detergents and disinfectants)). Food handling occupations are also prone to IgE-mediated protein contact dermatitis, immunological (IgE-mediated), and non-immunological occupational contact urticaria.
Specific exposures and elicitors in different food handling occupations are addressed in Sect. 3 (Specific Exposures) of this chapter. Some foods and food additives can trigger several of the above mechanisms independently and may induce different clinical pictures.
The prerequisite for a successful treatment is the individual identification and exclusion of the disease-eliciting allergen(s) as well as implementation of skin protection.
2 Epidemiology and Risk Factors of Occupational Skin Diseases in Chefs and Food Handlers
Chefs and food handlers are at high risk for developing an occupational skin disease (OSD) (mainly irritant contact dermatitis (ICD) or allergic contact dermatitis (ACD)). In a population-based study from Germany , the overall incidence rates of OSD per 10,000 workers per year were 33.2 for bakers, 23.9 for pastry cooks, 6.6 for cooks, and 2.9 for butchers and food processing industries .
An occupation with an incidence rate of more than 7 cases per 10,000 workers per year is considered an “exceedingly high-risk occupation” for an OSD, and those with 3–7 cases are considered “high-risk occupations” . In this register, overall the male gender was predominant concerning OSD in bakers, butchers, and the food processing industry, whereas in pastry cooks and cooks, the female gender was more frequent . In a previous analysis from the same register, it could be demonstrated that incidence rates were sex- and age-related : females developed OSD at higher incidence rates compared to males. OSD occurred mostly at a young age (between 15 and 24 years) after a median occupational exposure of 26 months in bakers and confectioners compared to 43 months in cooks .
These results were confirmed by a recent investigation from Denmark (analyzing the period 2003–2010): for females, the overall incidence rates of OSD per 10,000 workers per year were 88.6 for bakers, 31.4 for kitchen workers, 23.3 for cooks, and 22.7 for butchers . For males, the overall incidence rates of OSD per 10,000 workers per year were lower: 32.3 for bakers, 2.9 for kitchen workers, 17.5 for cooks, and 6.8 for butchers .
Further studies confirm that the food sector still belongs to the field of high-risk professions for OSD [4, 5, 6]: the relative risk of developing occupational contact dermatitis (OCD) in food-handling occupations is increased 3.37 times in Germany [4, 5]. The risk of OCD in various occupations was calculated on the basis of the proportion of documented cases in the Information Network of Departments of Dermatology (IVDK), years 2003–2013, per 100,000 persons in employment; for this purpose, the employment figures for the individual occupations were extracted from the databases of the Federal Employment Agency and the Employment Agency for December 2005 and 2010, respectively, and an average of both years was calculated. The mean risk of all patients was set to 1 as a reference [4, 5]. For women in the food sector, the risk for OCD is 5.38 times and for men 2.83 times increased . Bakers, pastry chefs, cooks, and meat and fish processors are mainly affected .
In a study from the European Surveillance System on Contact Allergies (ESSCA) network including data from the years 2002 to 2010 from 11 European countries, for food processing and related trades, a 3.08 times risk increase for OCD was identified (the risk assessment was based on the calculation of the risks of OCD, defined as the share of documented cases in the ESSCA network per 10,000 employed persons in a given occupation in all of the 11 countries participating in 2000) .
Young professionals from the food sector (predominantly bakers and pastry cooks) are at exceedingly high risk to develop an OSD, mainly ICD.
Of the different dermatological conditions caused by contact with foods (irritant contact dermatitis (ICD), allergic contact dermatitis (ACD), protein contact dermatitis (PCD), occupational contact urticaria (OCU), phototoxic and photoallergic contact dermatitis), irritant contact dermatitis is the most frequent OSD in chefs and food handlers [2, 5, 6, 7, 8, 9, 10]. However, the ratio of irritant versus allergic contact dermatitis varies between the different occupational fields : ICD was observed most frequently in pastry cooks (76% ICD versus 11% ACD and 7% combined ICD and ACD). In cooks, ICD was present in 69% of patients, ACD in 7%, and a “hybrid” contact dermatitis (a combination of ACD and ICD) in 13%. 63% of food handlers and butchers suffered from ICD, 13% from ACD, and 9% from a hybrid contact dermatitis. Compared to these occupational fields, in bakers, a higher rate of ACD was present: with a share of 53%, ICD was still the most frequent OSD among bakers, too; however, 23% had ACD and 17% combined ICD and ACD . A predominance in frequency of ICD over ACD in the respective food occupations was confirmed by a population-based survey of occupational hand eczema from Denmark  and from Germany  and ESSCA data analysis from 11 European countries , with one exception: in bakers from the German survey, ACD was present in 36.4% of patients versus ICD in 30.1% and “hybrid” contact dermatitis (a combination of ACD and ICD) in 4.2%. Overall – compared to earlier studies – in the recent surveys, the frequency of ICD and ACD seems to have converged to some degree: in the European survey , among bakers, pastry cooks, and confectionery makers with occupational contact dermatitis (OCD), detailed classification of OCD identified ICD in 40.5%, ACD in 18.3%, and a combination thereof in 8.7%. Among cooks with OCD, detailed classification identified ICD in 37%, ACD in 20.3%, and a combination thereof in 13.4% of patients. In the recent German survey , in cooks with OCD, 28.3% suffered from ICD versus 26.7% from ACD and 2.4% from a combination thereof, whereas among butchers with OCD, 45.5% had ICD, 29.1% ACD, and 5.5% a combination thereof.
Less frequently, due to protein contact with the skin, two IgE-mediated (sometimes overlapping) clinical conditions can be observed in chefs and food handlers: occupational contact urticaria (OCU) and protein contact dermatitis (PCD) [10, 11, 12, 13, 14, 15] (see also chapters “Protein Contact Dermatitis”, “Immediate-Type Hypersensitivity by Occupational Materials”, “Immediate Contact Reactions: Pathomechanisms and Clinical Presentation”). The frequency of OCU varies significantly with the group of patients examined: whereas Bauer et al. detected 1.5% of patients with OCU in a retrospective data analysis of patch test data of n = 873 employees in the food processing industry , up to 18.2% of butchers with occupational skin disease displayed OCU in a population-based survey of occupational hand eczema in Denmark . In the same survey, in bakers, 11.8% were diagnosed with OCU, and an additional 5.9% developed OCU based on ICD. In cooks and kitchen workers, OCU was present in 5.7%, and in an additional 10%, OCU and ICD were diagnosed . In a systematic clinical review on OCU caused by food  based on 72 patients (35 females and 37 males from 24 included studies), the occupations with far most cases were cooks (~75%) followed by bakers/pastry makers (~5%), butchers (~3%), and Shiitake growers (~3%).
Also in a retrospective review of patient files of the Finnish Institute of Occupational Health, during 1995–2011, the most common occupations of patients with immunological contact urticaria (CU) and/or PCD were chefs and bakers (n = 93/291; 32%) . Concomitant allergic airway disease caused by the same allergens was frequently found in these patients and should be routinely explored in patients with CU or PCD .
Whereas PCD is relatively rare in the general population, it is regularly seen in chefs and food handlers [14, 17, 18, 19, 20, 21]. PCD was diagnosed in 2.7% of n = 873 employees from the food-handling industries , and it was found that chefs who have to cook seafood are more at risk of occupational PCD than fishermen .
In a retrospective Danish study based on examinations, including skin prick testing and patch testing of patients with hand dermatoses occupationally exposed to foods, 57.0% had ICD, 22.0% had PCD, 2.4% had CU, and 1.8% had ACD .
An analysis of the IVDK database of n = 140.840 patients patch tested from 1994 to 2008 in the German-speaking countries revealed an overall frequency of PCD of 0.2%. In contrast, the frequency of PCD was 4% in bakers and pastry cooks, 1.9% in meat and fish processing industries, and 1.5% in cooks and caterers . Atopic eczema and irritant skin damage are predisposing factors for PCD . Patients with PCD were found to experience more severe and frequent consequences than patients with other food-related hand dermatoses : 75% of patients with PCD had to wear gloves at work, and 62.5% reported sick leave lasting for >3 weeks, as compared with 60.2% and 30%, respectively, of the patients with other occupational food-related hand dermatoses (p = 0.02). 62% versus 43%, respectively, had to change job because of skin problems (p = 0.02); atopic dermatitis was equally common in the two groups .
PCD is rare in the general population but commonly seen in chefs and food handlers. Atopic eczema and irritant skin damage are predisposing factors for PCD.
The percentage of atopic dermatitis (based on information about past flexural eczema or current atopic dermatitis diagnosed by a dermatologist) in the examined group of food occupations was 14–18% not higher than the percentage in the general population in a survey from Denmark .
Assuming an atopic skin diathesis (ASD) of 20% in the general population, the relative risk (RR) of an employee with an atopic skin diathesis developing OSD in one of the three occupations (baker, confectioner, cook) has been calculated to be increased in average by 3.6 times .
The potential impact of an atopic skin diathesis on OSD could be confirmed in food preparation workers (pastry cooks, bakers, cooks) in the context of preventive strategies: assuming a prevalence of 20% ASD in the total population, ASD accounts for about 50% (attributable risk (AR)) of the overall annual OSD incidence of 20.6 cases per 10,000 workers in pastry cooks. In consequence, at least half of this OSD rate could be prevented if ASD among the working population was surveyed . Similarly, the AR of an atopic skin diathesis to OSD was found to be 47.3% in bakers, 34.9% in cooks, and 24% in butchers and the food processing industry . However, it cannot be concluded from these data to discourage applicants with an ASD from entering risk occupations generally, because of the large number of applicants with this risk factor . In contrast, effective preventive strategies can be implemented including educational programs where individuals with an ASD are specially advised on skin protection and skin care measures . An atopic skin diathesis (>10 points, “Erlangen atopy score”), flexural dermatitis, or previous hand dermatitis (as the strongest factor) were predictive factors for the development of hand dermatitis in food industry apprentices, whereas no association was found to respiratory atopy, metal sensitization, or gender .
The need for and benefit of effective secondary preventive measures (exposure analysis-based individual and group training in preventive measures, protective gloves, and use of skin care and protection products) combined with medical treatment could be demonstrated in bakers and confectioners with occupational hand dermatitis .
An atopic skin diathesis (>10 points, “Erlangen atopy score”), flexural dermatitis, or previous hand dermatitis (as the strongest factor) are predictive factors for the development of hand dermatitis in the food industry.
3 Specific Exposures to Irritants, Contacts, and Protein Allergens in Chefs and Food Handlers
Chefs and food handlers have skin contact not only with foods and their innate ingredients (e.g., proteins and flavors) but also with added food additives and colors. Working standards for food handler hygiene, handwashing, and use of protective equipment [25, 26] implicate also frequent contact to water, cleaning agents, disinfectants, and rubber gloves which may cause irritant and allergic contact dermatitis as well.
3.1 Irritants in Food-Handling Occupations
Wet work (water and soap), foods (e.g., flour, vegetables, fruits, essential oils from spices, meat, fish), and disinfectants have been identified as relevant occupational exposures inducing irritant contact dermatitis [10, 27].
The foods that most commonly induce ICD are garlic, onion, citrus fruit, potatoes, sweetcorn, carrots, spices (e.g., cayenne pepper and jalapenos due to the irritancy of capsaicin), mustard, horseradish, radish, hot radish (syn. daikon radish), cabbage, cauliflower, broccoli (all due to the irritancy of allyl isothiocyanate), and pineapple (due to the irritant properties of bromelain) . Bromelain, the proteolytic enzyme found in pineapple juice, causes also a separation in the epidermis along with an increase in capillary permeability. The resulting histamine release causes pruritis and a wheal reaction . Bromelain is also used as a food additive that functions as flavor enhancer, flour treatment agent, and stabilizer (in fresh meat, poultry, and game, whole pieces or cuts) .
Some of the many food additives, which may irritate the skin, are acetic acid (E 260), ascorbic acid (E 300), citric acid (E 330), calcium acetate (E 263), calcium sulfate (E 516), lactic acid (E 270), sodium and potassium nitrate and nitrite (E 249–252 used as curing salts, antimicrobial preservative, color fixative in salted meats and fish, charcuterie, corned beef, hard cheese), and yeast [7, 27, 28].
Wet work and skin contact to disinfectants, foods, and food additives are of irritant potency in the food-handling occupations.
3.2 Contact Allergens in Food-Handling Occupations
Current predominant haptens in food-handling occupations are rubber ingredients (mainly thiurams), but also disinfectants (formaldehyde and glutaraldehyde) and Compositae plants which contain sesquiterpene lactones .
Sesquiterpene lactones are relevant contact allergens contained in artichoke, lettuce, endive, chicory, and chamomile . IVDK data from the years 1992 to 1999 had shown a frequency of sensitization to Compositae mix (CM) of 10% in cooks and 6.2% of employees from the food industry, respectively, both groups suspected of having occupational ACD . In contrast, prevalences of sensitization to Compositae plants in cooks might have decreased over recent years: in a stratified analysis of OCD performed in a IVDK subset of 1492 cooks and kitchen helpers, the prevalence was 2.1% (95% CI: 0.9–3.2) for CM I for the period 2007 to September 2011 and even lower from October 2011 to 2016 for CM II (0.8%, 95% CI: 0.2–1.4) . One could speculate that direct skin contact with vegetables, fruits, and spices from the Compositae family in cooking may have been reduced substantially by preventive measures .
As further relevant food-derived contact allergens, spices, flour, and other nonspecified allergens could be identified . Spice allergy usually presents as a contact dermatitis on the palmar sides of the fingers or hands . Of the approximately 60 spices and their essential oils used in cooking, over 20 are reported to be causes of ACD . Contact dermatitis has been most frequently described to the following spices (from different plant species): bay leaves (Laurus nobilis), cardamom (Elettaria cardamomum), cinnamon (Cinnamomum zeylanicum), cloves (Syzygium aromaticum), coriander (Coriandrum sativum), curry (a mixture of spices), mace (Myristica fragrans), nutmeg (Myristica fragrans), paprika (Capsicum annuum), turmeric (Curcuma longa), and vanilla (Vanilla planifolia) .
A number of fragrance materials contained in herbs, spices, and vegetables have been identified causing contact allergy in food occupations: anethole (synonyms: 1-methoxy-4-(1-propenyl)benzene and p-propenylanisole, a flavoring ingredient in anise, star anise, licorice and fennel), carvone (from spearmint), cinnamic acid (in cinnamon and tomato), cinnamic aldehyde (from cinnamon), citral (ginger), eugenol (in cloves, cinnamon, bay leave, Jamaican pepper), geraniol (from spearmint), limonene (from the peel of citrus fruits, dill, peppermint, spearmint, cardamom, caraway, celery seed oil, parsley, parsnips, and carrots), linalool (in basil and coriander), phellandrene (from ginger), pinene (from bay leaf, peppermint, spearmint, parsley, parsnips, celery, and carrots), and vanillin (from vanilla) [7, 27, 31]. Since contact dermatitis to spices is often based on contact sensitivity to a contained fragrant component, the patch test reactions to fragrance mix, balsam of Peru, and colophony may be positive and have been suggested as screening agents .
Carnosol, a phenolic antioxidant and tumor suppressant in extracts from rosemary, has been identified as contact allergen from rosemary. Urushiol, an oleoresin also present in poison ivy and poison oak, is the responsible contact allergen for mango dermatitis following the skin contact with the sap, fruit skin, leaf, or stem of the mango tree . Cardol, a phenol similar to urushiol, is contained in ginkgo seed and cashew nut oil .
Allyl isothiocyanate (mustard oil) is responsible for the pungent taste in mustard and horseradish. It is at the same time a sensitizer and irritant found in horseradish, cabbage, cauliflower, broccoli, brussel sprouts, kale, turnip, and radish [27, 31].
Due to the characteristic pattern of skin involvement (fingers DI to DIII of the nondominant hand), contact allergy to garlic (and therein contained contact allergens diallyl disulfide and to a lesser extent allylpropyldisulfide and allicin) remains the best known and recognizable of all forms of contact dermatitis in chefs [27, 33]. In a retrospective study from Spain investigating the incidence of ACD to plants, diallyl disulfide was the far most common allergen identified (47 confirmed cases in the 276 patients tested with this contact allergen (17%)) . Exposure was mostly nonoccupational (81% of cases, involving predominantly housewives). Cooks and restaurant employees were the occupations most frequently related (five cases). The most frequent clinical picture was a chronic hand eczema (91%), with a frequent specific involvement of the thumb, index, and middle finger of the nondominant hand. Consequently, diallyl disulfide should be tested in all housewives or cooks with chronic hand eczema , at least when cooking with Mediterranean, Arab, or Asian influences traditionally rich in garlic.
Predominant current uses in foods
Predominant type(s) of reaction
Acidic foods/beverages, candied/dried fruits, fruit and vegetable preparations, fermented foods, salads, vinegar, dairy and egg-based deserts
Acidic foods/beverages, candied/dried fruits, fruit and vegetable preparations, fermented foods, salads, vinegar, dairy and egg-based deserts
Fruit/vegetable purees, jams, juices, soft drinks, candy, milk, packaged meat/poultry/fish
Baked goods, cheese, meat/fish products, fruits/vegetables, pickles, juices, wine
Baked goods, cheese, meat/fish products, fruits/vegetables, pickles, juices, wine
Butylated hydroxyanisole (BHA)
Breakfast cereals, baked goods, beverages, butter oil, vegetable oil/fat; ghee, fat emulsions, lard, tallow, fish oil and other animal fats, spreads, confectionery, cocoa and chocolate products, decorations, toppings, ice cream, sherbet, desserts, milk powder, cream powder, frozen/canned/ fermented/dried/semi-preserved/smoked/salted fish and seafood, processed meats/poultry/game, dried vegetables, herbs, spices, seasonings, condiments, sauces, soups and broths, precooked pasta, chewing gum, processed nuts, potato snacks, yeast
As butylated hydroxyanisole
Indirect food additive: antimicrobial in sugarcane/beet sugar mills, food packaging adhesive and coating
Breakfast cereals, baked goods, mixes for bakery products and soups, sauces, butter oil, ghee, vegetable oil/fat, fat emulsions, spreads, confectionary, decorations, cocoa and chocolate products, herbs, spices, seasonings, condiments, precooked pasta, desserts, milk powder, cream powder, processed meats/poultry/game, fermented/dried/smoked/
salted fish and seafood, chewing gum, processed nuts, snacks (potato/cereal/flour/starch-based), whole/broken/flaked grains, rice, water-based flavored and energy drinks-based and energy drinks
e.g., sodium bisulfite (E 222)
Alcoholic beverages, vinegar, water-based flavored and energy drinks-based and energy drinks, fruit/vegetable juices/
concentrates, dried/canned/fermented/frozen fruits/vegetables, peeled/cut/shredded fresh vegetables, surface-treated fresh fruit, frozen/smoked/dried/fermented/salted fish and seafood, fresh seafood, jam, jelly marmalade, sugars, syrups, herbs, spices, seasonings, condiments, sauces, mead, mustard, starch, snacks (potato/cereal/flour/starch-based),
ACD, sulfite intolerance, urticaria upon ingestion (rarely spec. IgE)
butter oil, ghee, further oils and fats, dressings, desserts, chewing gum
Lard, tallow, fish oil, further animal oils, vegetable oils and fats, sauces, chewing gum
Dairy-based products, egg-based products, cheeses, fat spreads/emulsions, ice cream, sherbets, processed/cooked/canned fruits/vegetables, breakfast cereals, bakery products, soybean products, confectionary, precooked pasta and rice, processed meats/poultry/game, edible casings, seasonings, condiments, vinegar, mustard, sauces, soups, broths, salads, yeast, alcoholic beverages, water-based flavored and energy drinks-based and energy drinks, dietetic products, desserts
Karaya (=sterculia gum)
Acacia (=gum arabic)
Glaze of confectionary and fine bakery ware, decorations, toppings, sweet sauces, cocoa and chocolate products, coffee beans, surface-treated fresh fruits and nuts, chewing gum, water-based flavored and energy drinks
Glaze of confectionary, processed fruit, and as beeswax
Desserts, ice cream, milkshakes, sweetened condensed milks, sauces, pâtés and processed meat, soy products, diet drinks
Humectant, solvent for food colors and flavorings, chewing gum
Amaranth (=FD&C Red 2)c
Caviar, alcoholic beverages
Citrus red 2
Surface of oranges from Florida
Ponceau (=cochineal Red A)
Alcoholic beverages, water-based flavored drinks and energy drinks, dairy products, surface of cheese, canned fruits, fruit fillings/puree/spreads jams, jelly, marmalade, chewing gum, fine bakery ware, confectionary, surface decoration of chocolate, decorations, toppings, sweet sauces, ice cream, sherbet, syrups, desserts, surimi and fish roe, seafood, preserved/canned/fermented fish and seafood, edible casings, mustard, salads, sauces, seasonings, condiment, soups, broths, processed nuts, dietetic foods, surface labelling of eggs
Bakery products, bakery mixes, confectionary, water-based flavored drinks and energy drinks, ice cream, sauces, desserts, snacks, soups and broth, cereals, rice and pasta products, candy, chewing gum, jams, jelly, marmalade, gelatins, mustards, horseradish, yogurt, pickled products, fruit squash
Alcoholic beverages, water-based flavored drinks and energy drinks, dairy-based drinks, surface of cheese, breakfast cereals, fruit fillings/puree/spreads jams, jelly, marmalade, chewing gum, fine bakery ware, confectionary, surface decoration of chocolate, further decorations, toppings, sweet sauces, ice cream, sherbet, syrups, desserts, surimi and fish roe, fish, seafood, fish and seafood, edible casings, instant noodles, snacks, mustard, fermented vegetables, animal derived fats/oils, sauces, seasonings, condiment, soups, broths, dietetic foods
Alcoholic beverages, water-based flavored drinks and energy drinks, dairy products, bread products, batters, breakfast cereals, fruit fillings/puree/spreads jams, jelly, marmalade, surface of cheese, desserts, chewing gum, cocoa production, confectionary, decorations, toppings, sweet sauces, ice cream, sherbet, frozen/cooked/smoked fish and seafood, caviar, fish roe, mustard, sauces, soups, broths, snacks,
Surface labelling of eggs and further fresh foods
ACD; (spec. IgE, urticaria upon ingestion)
Multipurpose food additive (< 0.075%) for direct addition to food starch-modified, indirect food additive in industrial starche
Coating on fresh citrus fruits
Flour, whey products
Natural and synthetic flavors
Anise-like scent and taste in alcoholic drinks, seasoning and confectionery applications, natural berry extracts
Balsam of Peru
Contains about 200 components, which may be used in candy, chocolate, marzipan, bakery products, ice cream, desserts, water-based flavored drinks, liquors, aromatized tea
L-carvone (=R(−)-carvone): scent and taste of spearmint, D-carvone (=S(+)-carvone): scent and taste of caraway
Scent and taste of cinnamon (e.g., in ice cream, candy, beverages, chewing gum)
Scent and taste of cinnamon (e.g., in ice cream, candy, beverages, chewing gum)
Citral A (=geranial): strong scent and taste of lemon. Citral B (=neral): less intense but sweeter scent and taste of lemon
Spicy, clove-like aroma
Rose-like scent used in flavors such as peach, raspberry, grapefruit, red apple, plum, lime, orange, lemon, watermelon, pineapple, and blueberry
D-limonene (=R(+)-limonene) strong scent of orange
Floral scent with a touch of spiciness:
D-Linalool (=S(+)-linalool = coriandrol) is perceived as sweet and floral, whereas L-linalool (=R(−)-linalool = licareol) more woody and lavender-like
Vanilla taste. Used in ice cream, chocolate, confectionery and baked goods
Fertilizers, fungicides, herbicides, insecticides, lead, mercury
Eggplant, spinach, fermented foods, cheeses, alcoholic beverages, vinegars, microbial contamination of foods, histamine-releasing preservatives (e.g., benzoates)
Mushrooms, walnut, plantain, pineapple, banana, kiwifruit, plums, tomatoes, chocolate
Itch may occur after ingestion or as cofactor when skin barrier function is impaired (however, of lesser potency than histamine)
Cocoa, chocolate, soy beans, oatmeal, hazelnuts and almonds, fresh and dried legumes
Flares of ACD may occur after ingestionf
Fish, crustaceans, milk, dairy products, offal, dried fruits, nuts, condiment, oils, sugar, cereals (such as oats), broccoli and spinach
Flares of ACD may occur after ingestionf
Lentinan (i.e., a beta-glucan polysaccharide) found in shiitake
According to Section 21CFR172.892 as a food additive permitted for direct addition to food for human consumption for food starch-modified not to exceed 0.075% and sulfur dioxide not to exceed 0.05% [34, 35]
According to Section 21CFR178.3520 as an indirect food additive for industrial starch-modified not to exceed 0.3% or in alkaline starch not to exceed 0.6% 
Accordingly, industrial starch-modified may be used as a component of articles intended for use in producing, manufacturing, packing, processing, preparing, treating, packaging, transporting, or holding food, subject to the provisions of the respective section .
Consequently, concerning specific food additives, national differences in legislation and subsequent use and exposure at the workplace have to be regarded in the allergological evaluation.
In the United States, more than 3,000 additives are on file with the Food and Drug Administration of which more than half are regulated . In Europe, where in 2002 the EFSA (European Food Safety Authority) succeeded the Scientific Committee on Foods as the keystone of European Union (EU) risk assessment regarding food and feed safety, the European Parliament and Council Directives (94/36/EC) and (95/2/EC) and subsequent amendments used to determine the legal grounds for colors and additives in foods. These Directives are no longer in force (date of end of validity: January 20, 2010) and have been repealed by Regulation (EC) No 1333/2008 (and its amendments) of the European Parliament and of the Council on December 16, 2008, on food additives .
Sulfites are widely used as preservatives and antioxidants in the food industry. Legal regulations limit values and occurrence of sulfites in the food sector, and further occupational settings have been recently extensively investigated and reviewed [38, 39]. It is noteworthy to point out that often not the products themselves but rather the containers in which they are packed are treated with sulfites . They are known to trigger epidermal sensitizations and ACD; to identify these, patch testing is performed using sodium disulfite (=sodium metabisulfite, CAS 7681-57-4). In addition to this, inhalation or oral exposure to sulfite can cause the clinical picture of sulfite intolerance, including bronchoconstriction, urticaria, and cardiovascular, intestinal, and/or life-threatening anaphylactic reactions, the identification of which requires challenge testing. Despite the wide prevalence of sulfites as preservatives and antioxidants, the low number of cases documented in an occupational dermatological context suggests that at the present time, occupational sulfite exposure only rarely prevails in a disease-triggering manner .
Contaminants of foods of exogenous or endogenous/natural origin can complicate the process of identifying the offending agent . Difficulties in identifying these agents (which may not be listed on the food label (e.g., contaminants)) and obstacles in obtaining such substances for the allergological examination may occur. Furthermore, except for patch testing for allergic contact dermatitis, the diagnostic reliability of skin testing and in vitro tests with food additives is limited .
Compositae mix (food-related, since direct skin contact to Compositae like lettuce, chicory, endive, iceberg lettuce, artichoke, mugwort, etc. exists in food-handling occupations)
Thiuram mix (linked with preventive measures such as gloves)
Formaldehyde (contained in disinfectants and cleaning agents)
Nickel sulfate (which could be released from stainless steel cooking instruments) 
A broad sensitization to flavoring agents or spices in food processing occupations could not be confirmed in this retrospective analysis . Sensitizations to gallates, sulfites, and persulfates were only occasionally found [8, 38, 39].
For patch testing in food workers, patch testing of the standard, rubber, and Compositae series, as well as patients’ own products according to the individual history and exposure, is recommended . False-positive/irritant results may be obtained with nonstandardized patient-specific natural food materials and should be critically evaluated. If ethically and legally acceptable, in patch tests performed with nonstandardized foodstuffs, parallel testing in (at least three) control individuals may be considered [27, 42].
For patch testing in food workers, patch testing of the standard, rubber, and Compositae series, as well as patients’ own products according to the individual history and exposure, is recommended.
3.3 Elicitors of Phototoxic and Photoallergic Reactions in Food-Handling Occupations
Phototoxic reactions (“phytophotodermatitis”) may rarely occur in chefs and food handlers after skin contact with psoralen-containing plant material (e.g., fig, peel of lime, lemon, grapefruit, bitter and bergamot orange, carrot, celery, fennel, parsley and parsnip, dill, clove) and concomitant intense light exposure primarily in the UVA range 320–400 nm .
Photoallergic reactions in which the allergen is photo-activated by either sunlight or artificial light in the UVA range as a prerequisite to incite a delayed hypersensitivity reaction (mostly including the dorsa of the hands, extensor forearms, face, posterior neck, ears, “V area” of the chest, superior aspects of the back and shoulders) may rarely occur in chefs and food handlers after skin contact with foods and spices (e.g., garlic)  (see also chapter “Phototoxic and Photoallergic Reactions” and “Photopatch Testing”).
3.4 Elicitors of Protein Contact Dermatitis, Immunological Contact Urticaria and Nonimmunological Contact Urticaria in Food-Handling Occupations
Chefs and food handlers belong to the occupations at risk also for protein contact dermatitis (PCD) and occupational contact urticaria (OCU) (see also chapters “Protein Contact Dermatitis,” “Immediate-Type Hypersensitivity by Occupational Materials,” “Immediate Contact Reactions: Pathomechanisms and Clinical Presentation”) [17, 43]. OCU can be subdivided into two categories: immunological (IgE-mediated) due to foods or, more frequently, nonimmunological (NICU) due to a variety of low-molecular-weight substances such as preservatives, fragrances, and foodstuffs [44, 45].
Most potent and best studied food preservatives and flavoring triggering a NICU are benzoic acid, sodium benzoate, sorbic acid, abietic acid, nicotinic acid esters, cinnamic acid, cinnamic aldehyde, and balsam of Peru [7, 17, 27]. Furthermore, foodstuffs that contain a high genuine content of histamine (sauerkraut, pineapple, yeast, red wine, mature cheeses, pickled herring) and contaminated tuna, as well as those that cause direct release of histamine (strawberries, tomatoes, and alcohol), are often associated with NICU .
NICU (with few exceptions) remains restricted to the site of skin contact and rarely causes systemic reactions .
In contrast, IgE-mediated OCU may not be limited to the contact site but may present as a multisystemic disease (including generalized urticaria with or without angioedema, symptoms of the respiratory and gastrointestinal tracts, and as worst-case scenario anaphylactic shock) [46, 47].
Emergency treatment due to an anaphylactic shock at the workplace became necessary in five cases (16.7%) of a case series of 30 cooks (70% men) with an occupational seafood allergy . In this cohort, early manifestation of the disease (after median employment time of 1.7 years) was observed . In all except one case (96.7%), onset was localized on the hands. Most commonly documented were immediate sensitizations to cod, salmon, trout, and herring. In 27 cases (90%), discontinuation of occupation was needed and occurred after a median job period of 6.3 years .
A great number of relevant protein allergens causing IgE-mediated allergic reactions to foods have been identified on molecular grounds . For the current list of characterized food allergens, see the regularly updated official site for systematic allergen nomenclature that is approved by the World Health Organization and International Union of Immunological Societies (WHO/IUIS) Allergen Nomenclature Sub-committee (http://www.allergen.org) . During food processing (e.g., cooking), conformational epitopes of the protein allergen may be destroyed in many foods leading to a reduced allergenicity and reduced skin test reactivity of the cooked product in some patients. However, this cannot be generalized for all allergens and patients, since some allergens are heat-resistant (e.g., lipid transfer proteins (LTP) and seed storage proteins) and patients may be sensitized to linear epitopes as well which are less prone to modification during the cooking process. Scientific approaches to reduce the allergen content of tedious highly cross-reactive panallergens present in various plant foods (e.g., profilin; LTP) have been successfully addressed and resulted in profilin-reduced and LTP-reduced tomatoes, however, far from being marketed .
Besides NICU and immunological CU elicited by proteins of a vast spectrum of allergen sources, one peculiar disaccharide-triggered IgE-mediated allergy is worth mentioning due to its pathophysiological uniqueness: meat allergy associated with galactosyl-α-(1,3)-galactose (α-Gal). Elicitors are glycoproteins and glycolipids of non-primate mammalian species which contain the disaccharide galactosyl-α-(1,3)-galactose (α-Gal) . It is known that α-Gal is immunogenic in humans and causes glycan-specific IgG and also IgE responses of clinical relevance. The primary cause for induction of these IgE antibodies is tick bites which contain α-Gal in their gastrointestinal tract. In sensitized human individuals, α-Gal is associated with approximately 6h delayed anaphylaxis after ingestion of red meat or bovine gelatin or treatment with cetuximab, which all carry the specific disaccharide. Whereas work-related sensitization has been reported for forest workers , recently the first putative occupational case of α-Gal-associated recurrent delayed angioedema has been described in a chef . It seems feasible to take this disaccharide-triggered relatively rare disease entity into account as differential diagnosis in the assessment of OCU with or without angioedema and anaphylaxis in chefs and food handlers who taste dishes containing red meats and gelatin. α-Gal-specific diagnostic in vitro IgE tests are commercially available.
The same protein sources causing OCU may induce allergic respiratory symptoms and protein contact dermatitis [11, 14]. PCD in the food-handling occupations most frequently presents as a chronic or recurrent eczema which usually affects the hands and forearms [15, 21]. However, sometimes exclusively the fingertips or proximal nail folds (i.e., chronic paronychia) may be involved [11, 18, 43]. In distinguishing PCD from hand eczema of other origin-associated immediate symptoms of burning, itching, or stinging, few minutes after skin contact may be relevant [15, 21, 43]. A reduced stratum corneum barrier integrity (e.g., due to atopic dermatitis or irritant contact dermatitis) may facilitate penetration of high-molecular-weight proteins and induction of PCD [11, 18].
Diagnostic tests for IgE-mediated occupational skin diseases (OCU and PCD) include skin prick or scratch tests with the fresh and commercial material as well as in vitro tests for specific IgE (see also chapter “Skin Tests for Immediate Hypersensitivity”). Scratch and scratch-patch (scratch chamber) tests may be helpful in the individual case but bear a higher risk of irritant and false-positive reactions [11, 15, 21, 55]. Serially diluted allergens applied in prick and scratch tests are generally regarded as safe; however, since rarely systemic reactions may occur, for precautious reasons, a setting where trained personnel and resuscitation equipment are available is required. Some authors have recommended open skin application testing prior to the performance of prick and scratch tests since it is thought to be less hazardous than these more invasive methods [17, 18]. Placing or rubbing the food on intact skin usually is negative. Therefore, the importance of applying this test on damaged or eczematous skin has been emphasized [17, 18, 55]. The test substances are applied for 15–30 min to the skin, and readings are taken immediately after their removal as well as 30 and 60 min later . Suspected foods often give positive test results only with the native substances since commercial food extracts are often unreliable . For example, wheat and rye flour skin prick test (SPT) solutions from three companies for diagnosis of type I allergy in bakers differed extremely in protein concentrations and composition with the consequence of widely differing SPT results: sensitivity of SPTs in comparison with allergen-specific bronchial challenge as a gold standard for respiratory symptoms was between 40% and 67% (i.e., 33–60% of SPTs were false-negative) . This low sensitivity of commercial skin prick test solutions (including wheat and rye flour) was confirmed in a multicenter study carried out in 16 allergy centers in six European countries using standardized procedures . Furthermore, it was demonstrated that when performing skin prick tests with commercially available test preparations of occupational type I allergens, the optimal cutoff is reached at a wheal diameter ≥1.5 mm .
The EAACI position paper on skin prick testing in the diagnosis of occupational type I allergies  therefore concludes that depending on the case, small wheal sizes (≥ 1.5 mm) could be relevant and, after additional replication, the test result should be supported by serological IgE testing. Moreover, it is highly recommended to use SPT solutions from different manufacturers in parallel . Unfortunately, during the last few years, many marketing authorizations for test allergens for the diagnosis of occupational type I allergies have been withdrawn by the marketing authorization holders . Due to these limitations besides testing with several commercial SPT solutions at the time, skin prick testing fresh food materials (applied in a prick-to-prick) test is recommended [13, 15].
Food allergens causing IgE-mediated immediate-type reactions identified on molecular grounds are listed in the “The Official List of Allergens” provided by the IUIS (http://www.allergen.org).
Protein sources inducing PCD belong to four groups: (group 1) fruits, vegetables, spices, plants, and woods, (group 2) animal proteins, (group 3) grains, and (group 4) enzymes.
Despite the eczematous appearance of PCD, epicutaneous (patch) testing with the protein-containing foodstuff is negative in most cases. The diagnosis is based on a positive immediate reaction in the skin prick test, positive in vitro IgE findings, and/or a positive (re-)exposure history.
4 Conclusion for the Treatment of OSD in Chefs and Food Handlers
Chefs and food handlers belong to the group of occupations at (exceedingly) high risk for occupational skin diseases. A complex variety of occupational exposures to irritants, haptens, and protein allergens is linked with the food-handling occupations (as outlined above) and may result in seven different disease entities (ICD, ACD, immunological OCU, NICU, PCD and, rarely, phototoxic or photoallergic reactions). It should be kept in mind that the same substance can trigger several distinct mechanisms and may originate different clinical pictures in the affected individual.
The prerequisite for a successful treatment is the individual identification and exclusion of the disease-eliciting factors. Diagnostic procedures include, according to the patient’s history, patch testing of commercially available test series and individual foodstuffs, rub and/or skin prick tests, in vitro tests, avoidance, and/or provocation tests with the culprit substances/allergen(s) as well as an enduring implementation of a skin protection concept at the workplace.
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