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Pathophysiological variability affects the results of patch testing. In addition, even a minimal degree of test-imprecision due to this variability has a number of important statistical consequences for the analysis and interpretation of any patch test data set. One such statistical phenomenon that is often overlooked is the dependence of the positive predictive value (i.e., the predictive value of a positive patch test) on sensitivity and specificity, the impact of which is heavily dependent on the proportion of truly allergic subjects that are studied. A 2nd important issue is the fact that patch testing is performed in series, which means multiple tests. If we assume, for example, a patch test series of only 10 allergens, then it can be demonstrated that there is a random probability of over 40%) to find, simply by chance, for at least 1 allergen, a statistically significant difference between 2 groups of patients. Comparison of the results of series between patients calls for statistical adjustments in order to prevent erroneously positive differences and/or associations.

From 15 May to 15 December 1994, 2943 patients suspected of having contact dermatitis (1955 women, 988 men) were patch tested with methyldibromoglutaronitrile 0.3%, 0.1% and 0.05% pet. 119 patients (4.0%; women 4.1%, men 3.8%) proved to be allergic. 71% of the reactions were considered to be relevant. In 2/3 of the patients, causative products were cosmetics, in 1/3 moistened toilet tissues. Testing with methyldibromoglutaronitrile at lower concentrations (0.05% and 0.1%) and with commercial allergens (Euxyl K 400 and methyldibromoglutaronitrile, both containing methyldibromoglutaronitrile 0.1%), resulted in a number of false-negative reactions. All preservatives in the European standard series had lower scores than the 4% positive reactions to methyldibromoglutaronitrile (formaldehyde 2.0%, MCI/MI (Kathon CG) 3.2%, parabens 1.0%, quaternium-15 1.3%). It is concluded that methyldibromoglutaronitrile (present in the commercial preservative Euxyl K 400) is an important contact allergen in the Netherlands in cosmetics and moistened toilet tissues. It should be added to cosmetics series and to proctological series. The optimal test concentration is unknow, but may be 0.3% pet. The concentration of 0.1% methyldibromoglutaronitrile in the currently available commercial allergens appears to be too low, resulting in a number of false-negative reactions.

The purpose of the study was to evaluate a self-administered questionnaire on hand dermatitis that was developed to identify persons with hand dermatitis in epidemiological studies. A total of 109 nurses were subject to dermatological examination of the hands within 1 month of returning the questionnaire. 2 types of questionnaire diagnoses were made: a 'symptom-based' diagnosis and a 'self-reported diagnosis'. These were compared to the medical diagnosis of hand dermatitis. The prevalence of hand dermatitis in the 12 months before the study, based on the medical diagnosis, was 18.3%. The prevalence according to the symptom-based diagnosis and the self-reported diagnosis was 47.7% and 17.4%, respectively. The sensitivity and specificity of the symptom-based diagnosis were 100% and 64%, respectively. It is concluded that the symptom-based diagnosis can be used as screening instrument for the detection of cases in large study populations, if followed by dermatological examination of persons with a positive diagnosis. The sensitivity and specificity of the self-reported diagnosis were 65% and 93%, respectively. It is concluded that the self-reported diagnosis can be used to obtain a rough estimate of the prevalence, although comparison of prevalence figures between study populations may be distorted due to a difference in reporting of hand dermatitis. The results of the study illustrate the size of the differences in prevalence estimates that may arise as a result of differences in the definition and method of diagnosing hand dermatitis.

The influence of eccrine sweating on transepidermal water loss (TEWL) was investigated. TEWL was simultaneously measured on both forearms, with and without topical inactivation of the eccrine sweat glands by 0.3 ml of 0.5% aqueous scopolamine hydrobromide (HBr), applied under 1 h occlusive patches. The degree of sweat inhibition, after exercise, was measured at 2, 3 and 4 h after patch removal. In 42 out of 44 subjects, complete sweat inhibition (on exercise) was achieved only at 4 h after removal. After a 15-min rest in a room at 20 degrees C, the pre-exercise TEWL values (at 4 h) on the treated and untreated sites were not different (P greater than 0.05), in 38 out of 44 subjects. By this rest period, sweating due to slight physical, thermal or even emotional stimuli may be prevented in most subjects. In the other 6 subjects, the pre-exercise TEWL values (at 4 h) on the untreated site were 1-1.8 g/m2h higher than (P less than 0.001) on the treated site, due to emotional sweating. Thus, accurate baseline TEWL measurements may only be made after anticholinergic suppression of the sweat glands. In this way, accurate TEWL measurements may be made even outside favourable laboratory conditions, at industrial sites etc., where circumstances are far from ideal. The effect of this agent applied to a skin site previously irritated artificially by a 24-h occlusive sodium lauryl sulphate (SLS, 0.3 ml, 0.5% aq.) patch, was also investigated in 17 subjects. In all subjects, 4 h after removal, sweating (on exercise) was completely inhibited on the scopolamine-treated site, pre-irritated with SLS.(ABSTRACT TRUNCATED AT 250 WORDS)

A survey in 21 small metal factories in Singapore revealed that 6.6% of 751 workers (530 male, 221 female) had a skin disorder on their hands and arms. Dermatitis accounted for 4.5% (34 cases) and follicular rashes for 1% (8 cases). Positive patch tests were found in 23% (8 cases) of those with dermatitis and in 9.8% (21 workers) of a control group without any skin problem. Dermatitis was found to be associated with exposure to solvents. Simultaneous analysis of various exposure/risk factors by multiple logistic regression indicated a significant effect of combined exposure to oils and solvents (interaction). Being over 35 years of age was also a significant risk factor, whereas the rôle of contact allergy, detected by patch testing, was less pronounced.

A study was made of the comparability and reproducibility of the results of measurements of water loss, both in vitro and in vivo, using 4 ServoMed Evaporimeters (3 single-probe and 1 double-probe instrument). The optimum time for recording transepidermal water loss (TEWL) after the initial application of the probe to the skin (in vivo), and the best technique for optimizing the accuracy of measuring TEWL were determined. An evaporation device with a constant level of water loss was constructed for in vitro studies. The volar aspect of the right forearm skin of one subject was used in vivo. Both in vitro and in vivo measurements showed that there were some differences between the results of 4 of the 5 probes. The other probe was distinctly out of range. For all probes, the reproducibility of results of successive measurements was high. Stabilization of TEWL values was reached for all probes from 30-45 s after their initial application to the skin. It is recommended that TEWL be recorded for a further 30-s period, after the initial stabilization (45 s), and that this be taken as the true value. The manufacturer's recommended calibration procedure is based only on adjustments for the standard specified humidities and zero water loss. The importance of incorporating an additional calibration procedure which includes adjustments for an actual standard constant water loss is thus strongly stressed.

The rôle of different factors in the susceptibility of the skin to weak irritants was studied by means of multiple linear regression models. The skin of 37 healthy subjects was exposed to a solution of sodium lauryl sulphate of low molarity 2 x daily for 4 days. The condition of the skin was evaluated by transepidermal water loss (TEWL) measurements on the 1st day (before exposure, TEWL1) and on the 5th day of exposure (TEWL5), and by a visual scoring system. The TEWL5 value was strongly related to the TEWL1 value (R = 0.71). The influence of such factors as history of mucosal atopy, history of sensitivity to soap, dry skin, skin type, sex and age on the TEWL5 value was negligible. The baseline TEWL level (TEWL1) might be a reliable indication of an individual's susceptibility to weak irritants.

The purpose of this study was to develop a new model for the induction of chronic irritant contact dermatitis, which would reflect well the conditions of daily practice. Various weak irritant agents were tested for irritating potency on the skin and the sensitivity of transepidermal water loss (TEWL) measurements in the detection of early skin changes was also studied. 10 widely used surfactants and 1 solubilizer were applied to the skin of the forearms of healthy volunteers in aqueous solutions of 12.5 millimoles/l for 45 min twice daily for 3 weeks. The effect on the skin was evaluated daily by means of TEWL measurements and by a visual scoring system. Each solution caused an increase in TEWL value over time due to the cumulative irritating action on the epidermal barrier. This increase in TEWL was different for the various solutions, resulting in different mean TEWL values on the last day of the experiment. Thus, it was possible to rank the agents according to irritating potency. This ranking order was the same in almost every individual and remained constant during the 3 weeks. In comparison with the visual scoring system, the TEWL measurements were more sensitive in the detection of early changes in the skin.

An analysis of variance was conducted to estimate the intra- and inter-individual variations in TEWL on the forearms, by sites (8 measurement sites) and by days (10 different days), in 30 non-exposed healthy individuals. The estimated intra- and inter-individual variations, by sites, were 15.5% and 84.5%, respectively, the sum of the 2 components always being 100%. With the exclusion of the 2 most distal sites near the wrist, which had significantly higher baseline TEWL values and fluctuations in TEWL, an improvement in the intra-individual variation was obtained. Thus, of the 6 sites, the estimated intra- and inter-individual variations were 8.4% and 91.6%, respectively. This finding supports the exclusion of these most distal sites for future investigations. The estimated intra- and inter-individual variations, by days, were 20.6% and 79.4%, respectively. The low site-to-site (8.4%) and day-to-day (20.6%) intra-individual variations, as compared to the large inter-individual variations of the same (91.6% and 79.4%), indicate that baseline TEWL is a stable personal characteristic. Thus, individual susceptible to irritant contact dermatitis (ICD), due to occupational exposure, may be reliably characterized by utilizing their baseline TEWL values, for "prediction" of risk in epidemiological field studies.

Of 982 female clients of beauticians interviewed, 254 (25.9%) claimed to have experienced adverse reactions to cosmetics and toiletries in the preceding 5 years. Most reactions were caused by skin-care products (36.6%), followed by personal cleanliness products (29.5%), eye cosmetics (24.0%), deodorants and antiperspirants (12.6%), and facial make-up products (8.3%). 150 women were patch tested. In the European standard series, only a few positive reactions were seen to possible cosmetic allergens: fragrance mix (n = 3), wool alcohols (n = 3), formaldehyde (n = 2), balsam of Peru (n = 1), and colophony (n = 1). In the cosmetic series, only Kathon CG elicited positive patch test reactions (n = 3). Cosmetic allergy was considered to be "proven" in 3 patients (2.0%), and "possible" in 7 (4.7%). It is concluded that contact allergy is responsible for a minority (less than 10%) of all reactions to cosmetics and toiletries. The majority of reactions are due to irritation from personal cleanliness products such as soaps, shampoos, bath foams and from deodorants, or worsening of pre-existing dermatoses such as seborrhoeic dermatitis and acne.

The roles of the natural permeability of the stratum corneum to water, and the changes in that permeability effected by a single patch test, were investigated as parameters to predict the susceptibility of the skin to repeated exposures of an irritant. One site on the forearm skin of 27 non-atopic healthy subjects was exposed to a 0.5% concentration of sodium lauryl sulphate by a single occlusive 24-h patch. Another site was exposed to a twice daily 4-day repeated occlusive patch with the same irritant solution. The effects were evaluated by transepidermal water loss measurements made prior to the applications (baseline) on day 1 (BASE), following the single 24-h patch on day 2 (SINGL), and following the 4-day repeated applications on day 5 (REPET). Individuals with higher BASE had higher SINGL (R = 0.80, P less than 0.001) and higher REPET (R = 0.76, P less than 0.001). There was also a significant linear correlation between SINGL and REPET (R = 0.63, P less than 0.001). Multiple linear regression analysis of results, however, indicated that a high baseline TEWL is better indication of an individual's increased susceptibility (high REPET) to weak irritants than a high TEWL value following a single 24-h patch test. Baseline TEWL may therefore be used as a reasonably accurate preliminary "predictive" screening test for susceptibility to irritants.