ABSTRACT
Nickel sulfate remains the most common contact allergen with a standardized prevalence ranging from 19.7% (central Europe) to 24.4% (southern Europe) (1). The epidemiology of nickel allergy is currently changing in Europe following regulatory intervention on nickel release from consumer products (2). In the United States, the prevalence of nickel allergy is still increasing, which may be explained by the absence of regulations. The frequency of nickel allergy is approximately threefold higher in women than in men (3). Exposure to fashion jewelry is hypothesized as a major cause for this gender-based difference, and an increased susceptibility to contact sensitization in women is discussed controversially (4,5). Following cobalt (II) chloride, dichromate is the third frequent cause for metal allergy, showing variant frequency depending on the exposure [2.4% in the UK (west) vs. 4.5-5.9% in the remaining European Union (1). Overall, the prevalence of chromium allergy is still increasing in European countries as well as in the United States (2). Allergy and sensitization correlates with exposure to trivalent or hexavalent chromium, which is used by workers in the tanning, pottery, or metal industry, and by construction workers (6,7). In the case of, for example, construction workers, sensitization is caused by the water-soluble hexavalent chromate, which is one component of cement, a substance with alkaline, abrasive, and irritant properties (8). Professional exposure leads to an increase in the sensitization rate to 20% (9). However, in some Scandinavian countries sensitization rates in construction workers have currently been decreasing due to the addition of ferrous sulfate to cement, which was started more than 20 years ago (10). Since 2005, there has been a similar regulation in the European Union (11).
