Detection of occupational allergic contact dermatitis by patch testing

Occupational allergic contact dermatitis (OACD) is an important medical and occupational health problem. If undiagnosed, the disease may persist and even spread widely, resulting in severe and permanent disability to the worker, who may be deprived of his legal right to compensation. OACD is not uncommon in China, although many dermatologists fail to establish the connection between disease and working conditions, because they think that the diagnosis of OACD is the work of occupational medicine and that special diagnostic methods are required. The Ministry of Health and Ministry of Labour and Social Security of China have issued a new law recently to emphasize the prevention and treatment of occupational disease. It requires physicians to make an accurate diagnosis and report of occupation-related diseases. In this study, we have successfully investigated 14 cases of OACD in our hospital by patch testing the patients with a standard series of allergens and investigating by questionnaire the suspected offending occupational allergens. During a 2-year period (2001-2003), 14 patients with suspected allergic contact dermatitis were investigated and confirmed as having OACD. OACD may develop in many different occupations. In this study, nickel, 4-phenylenediamine, fragrance mix, black rubber mix, colophonium, epoxy resin and thiuram mix were identified by patch testing as the main offending allergens in such patients. These results indicate that patch testing plays a vital role in the diagnosis and identification of occupational allergens, and our study shows that OACD can often be diagnosed by patch testing patients with a standard series. The clinician should be alert to recognize the offending allergens of OACD by referring to patch testing all patients with clinically suspected contact dermatitis, and then educating the sensitized worker in how to avoid further exposure to the causative allergens.