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Shah M, Lewis FM, Gawkrodger DJ. Nickel as an Occupational Allergen: A Survey of 368 Nickel-Sensitive Subjects. Arch Dermatol. 1998;134(10):1231–1236. doi:10.1001/archderm.134.10.1231
To define the role of nickel as an occupational allergen.
Survey using patch-test results.
Contact dermatitis clinic in the university hospital of a large industrial British city.
Three hundred sixty-eight nickel-allergic patients seen during a 5-year period were assessed for the relevance of nickel contact in their workplace. Patients were divided into possible occupational nickel allergy and nonoccupational nickel allergy groups.
Nickel was considered an occupational allergen or possible occupational allergen in 84 (22.8%) of 368 patients shown to be nickel sensitive on patch testing. The main workers in whom nickel was a common allergen were hairdressers, retail clerks, caterers, domestic cleaners, and metalworkers. Those for whom occupational exposure was possible had a significantly higher prevalence of hand dermatitis compared with the nonoccupational nickel allergy group. Nickel allergy seemed to function as a secondary occupational influence, often in conjunction with other factors, such as irritants.
Although the overall importance of nickel as an occupational allergen cannot be easily assessed, there is evidence of its importance in some occupations, especially those involving wet work. The possibility that nickel is acting as an occupational allergen needs to be assessed on an individual basis, taking into account personal circumstances and environment, but particularly should be considered in patients with hand dermatitis.
THE ORIGINAL descriptions1,2 of nickel sensitivity were made in workers employed in the manufacture of nickel and in nickel plating. Sensitization and contact dermatitis from nickel can result from industrial exposure in the refining of the metal from its ores,3 in nickel plating,4,5 in the production of storage batteries, in the manufacture of some types of enamel or glass,6 and in certain chemical processes where nickel catalysts are used.7 In these industries, nickel-tolerant workers tend to be selected by a process of elimination or, in some cases, nickel-sensitive subjects are excluded by a policy of preemployment patch testing using a nickel salt. Improvements in industrial hygiene have also been made, so that nickel sensitivity, common in nickel platers before 1930, is now relatively uncommon in that group,4,8,9 apart from certain isolated outbreaks.5 Nonetheless, in a large demographic study10 of industrial dermatoses, nickel was found to be the predominant occupational allergen in women and one of the 10 most common in men.
The majority of cases of nickel allergy are now thought to be caused by ear piercing and the wearing of nickel-plated jewelry.11,12 Subjects who have been sensitized to nickel by nonoccupational means are being exposed to nickel in the course of their work, and they, in some instances, develop an allergic contact dermatitis. This type of "secondary" exposure may be difficult to identify because there are often other factors involved, such as the effect of irritants or the coexistence of atopy. However, nickel is undoubtedly of some importance as a contact allergen in a number of occupations. High exposure to nickel may occur in cashiers and retail clerks,13,14 hairdressers,15,16 metalworkers,17 domestic cleaners,18 food handlers,19 bar workers,20 and painters.21 Many of these workers are involved in wet-work occupations. The fluids to which they are exposed are capable of leaching nickel out of utensils.22-24 Evidence of nickel as a contaminant in cutting fluids may be found in a number of industrial processes, and high levels of nickel have been demonstrated in samples of used cutting oils.25 In hairdressing, permanent wave solutions containing ammonium thioglycolate can leach appreciable amounts of nickel from nickel-plated objects, such as scissors.26 In addition, nickel may be released from stainless steel saucepans at acid pH.27,28 Nickel may also be released from some stainless steel products. Stainless steel tools have, in the past, been considered safe, as the amount of nickel they release is small.29 However, it has been found29 that stainless steels with a high sulphur content (known as American Iron and Steel Institute standard 303 steel) can release sufficient nickel to cause contact dermatitis in nickel-sensitive subjects. It has also been found that aluminum finished by "cold impregnation" with nickel, a technique that converts the surface of metallic aluminum to an unreactive state, can cause a dermatitis in nickel-sensitive subjects.30
Rarely, nickel has been reported as an occupational allergen in tailors, seamstresses,31,32 pottery workers, workers who manufacture margarine, butchers, musicians and teachers who handle chalk,7 construction workers,33 workers who manufacture brick,34 and workers in certain chemical factories.35 In this study, the role of nickel as an occupational allergen in 368 patients shown to be allergic to nickel on patch testing is assessed. In addition, the importance and relevance of nickel as an occupational allergen in various occupations is discussed.
The records of 1972 patients (1265 female and 707 male), referred to our Contact Clinic and receiving routine patch tests between January 1991 and December 1995, were examined. At their first attendance, information was collected regarding basic demographic details, current site of disease, any atopic symptoms, present and previous occupation, and history of hand dermatitis. Patients were tested with the European standard series of patch tests (Trolab, Hermal Kurt Hermann, Hamburg, Germany) with additional series applied depending on the clinical situation and the patient's occupation. The patches were left on for 2 days and read at 2 and 4 days, according to standard practice. Definite allergic reactions were graded from weak positive (+) to extreme positive (+++), according to the definition of the International Contact Dermatitis Research Group.
For any patient who was allergic to 5% nickel sulphate in petrolatum, an assessment was made by 2 observers together (M.S. and D.J.G.) of whether nickel might be acting as an occupation allergen and whether the patient may have been sensitized to nickel by industrial exposure. The following factors were taken into account to assess the relevance of nickel allergy in the workplace: (1) the probability of exposure to the allergen during the course of the individual carrying out his or her occupation; (2) the characteristics of the eruption being compatible with that of a contact dermatitis; (3) the distribution of the dermatitis being such that it would be compatible with the pattern of occupational exposure; and (4) the exclusion of other factors that could be responsible for a dermatitis of the appearance and distribution to that seen, or the likelihood that any such factors are of lesser importance than exposure to the allergen.
On the basis of these criteria, patients were divided into 1 of 2 diagnostic groups: possible occupational nickel allergy and nonoccupational nickel allergy.
In the possible occupational nickel allergy group, patients had definite exposure to nickel-containing items in the workplace. In this group, clinical history was sufficient to discover occupational nickel sources. Other contact allergies, irritant factors, or endogenous dermatitis were thought to be of lesser importance. In the nonoccupational nickel allergy group, there was little or no exposure to nickel at work, or there were other contact sensitivities, irritant factors, or endogenous eczemas that were of overriding importance.
In a minority of cases, it was not obvious whether patients had been exposed to nickel through contact with items at work. In these cases, metal implements used routinely at the workplace were brought to the dermatology department and spot tested using a 1% dimethylglyoxime–10% ammonium hydroxide solution. A positive result is shown by the formation of a pink area on the surface of the metal. In the nonoccupational nickel allergy group, lack of nickel exposure was determined by clinical history alone.
Patients in whom nickel sensitivity was thought to be clinically relevant were given detailed advice as to what objects contained nickel, with particular relevance to potential occupational exposure. However, day-to-day avoidance of nickel is difficult even when nickel-containing materials can be identified.
Of 1972 patients, 368 (336 female and 32 male) gave a definite allergic positive reaction to nickel sulphate on patch testing, and these were all included in the study. Ages ranged between 7 and 81 years (mean, 35.5 years). A total of 152 patients were evaluated at the initial examination as having a hand dermatitis (hand alone, 74; hand and foot, 23; hand and face, 29; hand and arms, 15; hand and another site, 11). In the other 216 patients, the face was affected in 107, the arms in 15, and the legs in 9. In 32 patients, the eruption was generalized, and, in 53, other sites were affected. One hundred seventy-three patients gave a personal history of 1 or more types of atopy (asthma, 57; hayfever, 93; atopic eczema, 92). Three hundred thirteen subjects had a history of reacting to jewelry or to other metal-to-skin contact (mean age at onset, 21.2 years), and 316 had a history of ear piercing (mean age of piercing, 17.1 years). One hundred eighty-seven patients gave a previous history of hand dermatitis.
One or more allergens (in addition to nickel) were found in 254 cases, of whom 108 patients were allergic to 1 or more metals in addition to nickel. The positive reactions to other metals occurred in the following numbers of patients: palladium, 54; cobalt, 54; gold, 15; chromium, 10; mercury, 8; and platinum, 1.
Each of the 368 nickel-sensitive subjects was classified into 1 of 2 groups. Eighty-four patients (22.8%) were classified as having possible occupational nickel allergy, and 284 were allocated to the nonoccupational nickel allergy group. The mean age of the possible occupational nickel allergy group was 34.2 years (range, 18-84 years). The mean age of the nonoccupational nickel allergy group was 38.4 years (range, 14-86 years). The 2 groups were compared regarding various clinical features (Table 1). The possible occupational nickel group differed from the nonoccupational nickel allergy group in having a statistically significant higher prevalence of hand dermatitis (P<.001). However, there were no significant differences between the 2 groups regarding sex, history of asthma or atopic eczema, history of skin reactions to jewelry or metals, or the existence of coallergens. The incidence of hayfever may have been slightly greater in the possible occupational nickel allergy group, but this was of borderline significance (P=.09).
The most common occupations in the possible occupational nickel allergy group were retail clerks, hairdressers, domestic cleaners, metalworkers, and caterers (Table 2). Statistically, there was no significant difference between individual occupational groups because of the relatively small numbers in each group. However, we used hierarchical cluster analysis with the χ2 value as our distance. In this way, combined groups were selected according to between-groups linkage. This type of analysis has its limitations, but gives an impression of statistical trends. A dendrogram with 4 subgroups was plotted. In the first group, including retail clerks, hairdressers, bar workers, bakery workers, garment factory workers, and bank clerks, there was a highly statistically significant difference between the possible occupational nickel allergy patients and nonoccupational nickel allergy patients (P<.001). A similar result was obtained for the second group, including domestic cleaners, metalworkers, caterers, and factory packers (P<.001). The third group, including office workers, unemployed people, house workers, students, nurses, those in education, retired people, and other occupations, demonstrated no significant differences between the possible occupational nickel allergy and nonoccupational nickel allergy groups. Finally, in the fourth group of dental staff and laboratory technicians, there was a highly statistically significant difference (P<.001).
In the possible occupational nickel allergy group (n=84), workers had significant nickel contact that was felt to be relevant to their symptoms of dermatitis. Twenty subjects worked as retail clerks, of whom 2 worked in jewelry shops and handled metal jewelry and money. The other 18 retail clerks handled considerable numbers of metal coins on a daily basis. There were 17 hairdressers, all of whom used nickel equipment and nickel-plated scissors. There were 12 domestic cleaners, 2 of whom had previously been hairdressers, and 8 caterers. They handled metal objects and equipment in the course of their work. Among the 8 metalworkers, the following work was performed: welding, nickel electroplating, machine operating (wires and metal alloys), engineering (metal alloys), lining steel furnaces, pattern making (metal sheets), metal cutting, and cleaning nickel-plated scissors. There were 3 factory packers, all of whom packed metal items. These included nickel-plated scissors, nickel alloys, and nickel-plated fittings. Three subjects who were employed in bar work or as waiters handled large quantities of money as part of their job. Two subjects worked in bakeries, both handling metal utensils and coins. Two office workers had symptoms relevant to an occupational nickel allergy. One had a dermatitis related to sucking nickel-containing paper clips, and the other handled coins. The possible occupational nickel allergy group also contained 2 dental workers who handled nickel-plated equipment, a laboratory technician who handled nickel salts, a bank worker who handled large quantities of coins, and a woman who did not currently work outside the home whose dermatitis had begun when she worked as a hairdresser. In addition, there were 2 garment factory workers who handled nickel-plated equipment and 2 unemployed subjects, both of whom had had previous nickel exposure. One had been a metal miller, and the other was previously an engineer.
Nine of the 84 patients with a possible occupational nickel allergy were men. All were exposed to nickel in their work. Seven worked in the metal industry. Their occupations were pattern making (working with metal sheets), welding, metalworking (for 2 men, one was involved in cutting nickel alloys, the other made nickel-containing parts for light bulbs), driving (moving loads of nickel alloys), engineering, and working on the linings of steel furnaces. Two of the men worked outside the metal industry. One was a domestic cleaner, and the other was a shopkeeper who was exposed to large numbers of coins.
An assessment of the relevance of nickel as a contact allergen is difficult. Proving the importance of nickel as a contact allergen has always been difficult, especially in view of this high background of contact sensitivity. Moreover, since nickel is ubiquitous, total exclusion at the workplace and at home is virtually impossible.
We have attempted to categorize nickel allergy according to occupational group. In the majority of patients reacting to nickel on patch testing, their occupation has little or no relevance. However, we felt that nickel was possibly an occupational allergen in 84 (22.8%) of 368 patients, taking into account multiple factors. Occupational nickel allergy appears to be associated with hand dermatitis. Other factors, such as age, sex, atopy, history of jewelry dermatitis, and reactivity to other allergens, are not relevant in this series. It is difficult to determine the exact role of nickel in certain subjects. For example, in the metalworkers, nickel was the major allergen in each of the affected patients and, undoubtedly, was the most important etiological factor in their dermatitis. However, in other occupational groups, such as retail clerks, nickel seemed to play a significant part in the cause of their dermatitis, but may not have been the major etiological factor. It is important to establish the difference between occupational sensitization and secondary dermatitis from nickel contact. This can often be determined by taking a careful and detailed history.
The categorization of patients on clinical judgment may lead to some degree of subjective error. We have attempted to reduce this error by taking a number of clinical and occupational factors into account, ie, present and previous occupations with regard to nickel exposure, contact with irritants, role of additional allergens, atopy or other endogenous dermatoses, and clinical factors, such as distribution of the dermatitis. Unfortunately, there is no specific formula for determining the exact relevance of a contact allergen, the best measure perhaps being the improvement of dermatitis on allergen avoidance. In the case of nickel, allergen avoidance is virtually impossible, and this compounds the difficulty of assessing the role of nickel in industrial dermatitis. Occupational dermatitis is often caused by more than one etiological factor. Clinical judgment may suggest that an allergen such as nickel is of some significance, but it is frequently difficult to state the degree of importance. Although statistically we can demonstrate certain occupational groups are more prone to be associated with nickel sensitivity, each case needs to be assessed on its individual merits. It is not possible to be proscriptive about the professions in which nickel may act as an occupational allergen. Using our selection criteria, hand dermatitis is often an important factor when deciding whether a dermatitis may be occupationally induced. The hands are the area of the body most exposed to environmental factors during the course of work. However, occupational dermatitis may also be present, according to the allergen to which the skin is exposed, on the forearms, thighs, lower legs, feet, or face. Nickel occupational dermatitis, however, would be expected to primarily involve the hands. Other selection criteria were important in determining whether the subject's dermatitis was occupational or nonoccupational, including not only the potential for exposure to the allergen and the morphologic nature of the eruption, but also exclusion criteria, such as the dermatitis being primarily that of an atopic or irritant type or a contact dermatitis principally caused by another allergen.
We did not attempt to determine the proportion of subjects who had been sensitized to nickel at work. The number occupationally exposed to nickel salts in solution is fairly small, but many have had contact with nickel in metallic form; it is likely that some will have been sensitized by handling coins or nickel-plated utensils. However, most nickel-allergic patients appear to have been sensitized by ear piercing and exposure to inexpensive costume jewelry,11 and the majority of occupational nickel problems seem to be the result of secondary contact rather than to follow primary sensitization.36
The presence of hand dermatitis in a patient with nickel allergy raises the possibility that nickel may be acting as an occupational allergen. The relevance of contact allergy to nickel for cashiers, caterers, domestic cleaners, and hairdressers with hand dermatitis has been questioned. In money-handling occupations, such as cashiers and retail clerks, nickel from coins may be implicated as a relevant allergen. In some subjects,13,37 provocation tests have been positive. However, nickel-sensitive cashiers who handle coins do not inevitably develop a hand dermatitis,14 and it has been suggested that contact with water or other irritants may be a predisposing factor toward this occurrence.37
There is agreement that nickel sensitivity in hairdressers is common,16,38-40 but there is disagreement as to whether it is relevant to their dermatitis. Most authors16,38 agree that female hairdressers are sensitized by ear piercing rather than by occupational exposure to nickel. However, secondary contact sensitivity to nickel is probably of importance in hairdresser's hand dermatitis.15,40 A similar problem exists for cleaners and caterers. Nickel allergy is frequent18,41 and usually predates employment in the field. In some cases, nickel has been believed to be relevant, since cleaning water may contain high levels of nickel.18
Although most nickel-sensitive subjects experience only a cosmetic nuisance from their allergy, in some patients occupational nickel allergy plays a significant role in their dermatitis. Assessment of each case is needed to determine the relevance of nickel as an occupational allergen. Nickel allergy is common, and, with a view to preventing this type of secondary contact dermatitis, the European Union has followed the lead shown by Denmark by introducing legislation to limit the amount of nickel in jewelry worn next to the skin.41 Other forms of prevention of nickel allergy are possible in the workplace. There is renewed interest in the effect of topical chelating agents or ion exchangers to bind nickel and prevent it from penetrating the skin in situations where nickel is known to be present.42,43 The occupational importance of nickel allergy is difficult to determine. Our finding that nickel may be a significant occupational factor in nearly a quarter of our nickel-allergic patients suggests that its role as an occupational allergen is underestimated.
Accepted for publication May 18, 1998.
Jean Russell, BSc, helped with the statistical analyses. We thank colleagues who helped complete clinic data sheets and staff of the Clinical Audit Department at Royal Hallamshire Hospital, Sheffield, England, for computer data entry.
Corresponding author: David J Gawkrodger, MD, Department of Dermatology, Royal Hallamshire Hospital, Sheffield S10 2JF, England (e-mail: firstname.lastname@example.org).