Simultaneous sodium lauryl sulphate testing improves the diagnostic validity of allergic patch tests. Results from a prospective multicentre study of the German Contact Dermatitis Research Group (Deutsche Kontaktallergie-Gruppe, DKG)

Background There is evidence that a higher skin susceptibility may induce nonspecific erythematous or weak positive reactions to contact allergens in patch testing. Objectives To evaluate whether simultaneous application of sodium lauryl sulphate (SLS) along with diagnostic patch tests with contact allergens can provide information regarding skin irritability which may help to discriminate allergic from nonspecific irritant reactions to contact allergens. Methods Between July 2001 and June 2003, this prospective study collected patch test data of 5971 patients from 19 centres in Germany and Austria in the Information Network of Departments of Dermatology (IVDK). In addition to contact allergens (standard series and eight known ‘problematic’ allergens with a low reaction index and a high positivity ratio: 1,3‐diphenylguanidine, amerchol L‐101, benzalkonium chloride, benzoyl peroxide, cocamidopropyl betaine, octyl gallate, phenyl mercuric acetate and propylene glycol), patches with SLS 0·5% and 0·25% aq. were applied. Reactions to the allergens and to SLS were analysed at the IVDK data centre. The association between an erythematous or positive reaction to a certain allergen and an irritant reaction to SLS was assessed with logistic regression analysis, at the same time controlling for the influence of age and sex. Results Of the 29 allergens of the standard series, 23 and 21 gave a higher percentage of nonspecific erythematous reactions in patients with an irritant reaction to 0·25% and 0·5% SLS, respectively, in comparison with SLS‐negative patients. All eight ‘problematic’ allergens gave an increased percentage of nonspecific erythematous reactions. Similarly, 22 and 21 allergens of the standard series gave a higher percentage of positive allergic reactions in patients with an irritant reaction to 0·25% and 0·5% SLS, respectively, and seven of the eight ‘problematic’ allergens gave a higher percentage of positive allergic rections (exception: octyl gallate). For most allergens, the markers of skin reaction (reaction index and positivity ratio) were worse in SLS‐positive patients. Differences were more pronounced when testing with SLS 0·25% than with SLS 0·5%. Conclusions Because there is a convincing association between skin irritability (evaluated by SLS test) and the degree of skin reaction to contact allergens, the SLS test may help in deciding whether a doubtful erythematous or weakly ‘positive’ skin reaction should be interpreted as allergic or irritant.     

Primin standard patch testing: 5 years experience

From 1 November 1984 to 1 November 1989. 3075 patients (1949 female and 1126 male) were patch tested with the European standard series, including primin 0.01% pet. 57 positive reactions were obtained (1.8%). About 95% of the patients with positive patch tests were female. 60% of the patch-test-positive patients were above age 60 and 35% above 70 years. The test was negative in all under the age of 20 and rarely positive under the age of 35 years. Only 2 patients had probable patch test sensitization observed 8 and 14 days after application of the test material. 41% of the patients with positive reactions had current primula dermatitis at the time of patch testing. The frequency and high degree of current relevance justify inclusion of primin in the standard series, at least in certain geographical regions. The patch test concentration of 0.01% pet. seems to be correct.     

The results of ingredient patch testing in contact dermatitis elicited by povidone-iodine preparations

10 cases of contact dermatitis which began during the application of povidone-iodine preparations were examined with patch tests using 2 kinds of povidone-iodine preparations and their ingredients, i.e., povidone-iodine, polyoxyethylene nonylphenyl ether and glycerin, and also the components of povidone-iodine, i.e., iodine and polyvinylpyrrolidone. All 10 cases reacted positively to the povidone-iodine preparations and povidone-iodine, 3 out of the 10 to polyoxyethylene nonylphenyl ether, 1 out of the 9 tested to iodine, while no positive response was found to glycerin or polyvinyl-pyrrolidone. It was difficult to distinguish between allergic responses from irritation, as responses to patches of povidone-iodine and its preparations usually include irritation at high frequencies. Based on comparison of results with a control group, however, those showing + or stronger reactions to 2% povidone-iodine at days 3 to 5 were considered to be allergic. Thus, 4 out of the 10 cases were considered as sensitization to povidone-iodine. Another 3 cases were found to be polyoxyethylene nonylphenyl ether sensitized, and another 1 iodine sensitized, while the patch test reactions of the other 2 were considered to have been elicited by irritation.     

Allergic and irritant patch test reactions and atopic disease

This study presents a profile of patients with chronic recalcitrant eczematous disease referred by dermatologists for contact allergy evaluation. Allergic contact dermatitis (ACD) and irritant responses were carefully defined, as was the presence or absence of atopy obtained by history. Of 410 patients studied, 44% had no history of atopic disease and 46% were classed as definitely atopic. Among relevant ACD patch lest reactors ( n = 198). 51.5% had atopy, compared with 40.9% with no atopy but this difference was not significant. Likewise, among atopics ( n = 189). 54% had definite, relevant ACD patch test responses while 33.9% had negative ACD (again not significant). Significance was seen in the higher mean number of positive allergic patch tests in the atopic group (2.7 versus 2.0. p =0.0223). Irritant patch tests were highest among patients with both ACD and atopy ( p = U.0308) and the proportion of irritant responses correlated with increasing numbers of positive ACD tests. We conclude that atopics are at least as likely to have ACD as are non-u topics. Irritancy is increased in these patients with chronic dermatitis and the frequency of irritant reactions correlates with both greater numbers of ACD responses and with presence of atopy.     

Patch testing with the irritant sodium lauryl sulfate (SLS) is useful in interpreting weak reactions to contact allergens as allergic or irritant

Several contact allergens are tested at concentrations which might cause irritant reactions. In this study we investigated whether the reactivity to a standard irritant is useful in identifying subjects with hyperreactive skin yielding a higher rate of doubtful or irritant reactions. Sodium lauryl sulfate (SLS) 0.5% (aqua) was tested in addition to the standard series routinely for 5 years in the Department of Dermatology, Dortmund. For data analysis, we compared reactions at D3 to the standard series, the vehicle/emulsifier and preservative series and benzoyl peroxide to the reactions obtained with SLS. Proportions were standardized for age and sex. The association between reactivity to a certain allergen and SLS reactivity as a dichotomous outcome, controlled for age and sex as potential confounders, was assessed with logistic regression analysis. Results showed that of the 1600 tested patients, 668 (41.8%) had an irritant reaction to SLS which exceeded 2 + in only 41 patients. Seasonal variation was statistically significant, showing reduced SLS reactivity in summer vs. winter. Patients with irritant reactions to SLS showed significantly more erythematous reactions to the following 10 allergens of the standard series: fragrance mix, cobalt chloride, balsam of Peru (Myroxylon pereirae), lanolin alcohol, 4-phenylenediamine base (PPD), propolis, formaldehyde, N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), benzocaine, and 4-tert-butylphenol-formaldehyde resin. No significant differences regarding strong positive allergic reactions were observed. Concerning other allergens, significantly more erythematous reactions were observed in SLS-reactive patients to benzoyl peroxide, octyl gallate, cocamidopropyl betaine, Amerchol L-101, tert-butylhydroquinone, and triethanolamine. In the SLS-reactive group of patients, the reaction index was negative for 10 allergens of the standard series compared to only 5 in the SLS non-responder group. For the first time, this study, based on a large data pool, revealed a significant association between reactivity to the irritant SLS and erythematous reactions to certain allergens. With SLS as a marker for hyperreactive skin at hand, some of these reactions can now be classified as irritant more confidently, particularly if there is no history of exposure to the allergen.     

Petechial reaction following patch testing with cobalt

A total of 132 patch tested patients reacted with petechial reactions to cobalt chloride 1 % in petrolatum; 23 were retested with various concentrations of cobalt. In about 60% of those retested the petechial reaction could be reproduced. Histopathological examination showed slight perivascular tymphocytic infiltration, swollen endothelium and extravasation of erythrocytes but no signs of vasculitis.
It is suggested that in predisposed patients the petechial reaction following patch testing could be the result of primary irritation.     

Allergic contact dermatitis due to phenylephrine hydrochloride, with an unusual patch test reaction

2-day (2-D) closed patch tests are often used in daily clinical practice and useful for evaluating the cause of allergic contact dermatitis. However, even when 2-D closed patch tests at appropriate concentrations are performed for suspected allergic contact dermatitis based on clinical findings, positive reactions are not always obtained. Therefore, although the use of the allergen again induces similar symptoms, a definite diagnosis cannot be made in some cases. We report a case of allergic contact dermatitis due to phenylephrine hydrochloride in eyedrops, with an unusual patch test reaction. Although the results of the routine 2-D closed patch test were negative, a definite diagnosis could be made by closed scratch-patch test. In addition, long-lasting allergic patch test reactions were observed at the positive scratch-patch test site for about 3 months. We speculated that these unusual results on patch testing in our case were associated with the degree of percutaneous absorption of causative agents. Therefore, even when 2-D closed patch tests are negative, scratch-patch tests may be indicated for patients in whom clinical symptoms continue strongly to suggest contact dermatitis.     

Formaldehyde concentration in diagnostic patch testing: comparison of 1% with 2%

Exposure to formaldehyde is common from both consumer products and industry. The reliability of the patch test is essential for the diagnosis of formaldehyde allergy as it is difficult to suspect from the patient's history. The recommended formaldehyde patch test concentration has been reduced over the last decades from 4–5% to 2% and is currently 1%. The changes have not been based upon formal studies, but driven by an intention to reduce irritancy and false-positive results. The aim of the present study was prospectively to compare the outcome of simultaneous testing with formaldehyde 1% and 2% in consecutively patch-tested patients, with respect to frequency of positive patch test reactions, strength of patch test reactions to different formaldehyde test concentrations, irritancy and relevance. The study included 3734 consecutively patch tested patients. 121 gave a positive reaction to 1% and/or 2% formaldehyde in water. There was no statistically significant difference between 1 and 2% with respect to allergic reactions, but 2% gave significantly more irritant reactions. Doubtful, positive and follicular reactions at day (D) 2 frequently developed into true positive reactions at D 3 to 4. Reading at D 7 gave few additional positive cases compared to D 3/4. Problems related to relevance are discussed. Based on present knowledge, a 1% patch test concentration for formaldehyde is recommended.     

The MOAHLFA index of irritant sodium lauryl sulfate reactions: first results of a multicentre study on routine sodium lauryl sulfate patch testing

In a multicentre study of the German Contact Dermatitis Research Group, sodium lauryl sulfate (SLS) 0.25% and 0.5% aq. has been added to routine allergen patch tests to assess its properties as a convenient diagnostic indicator of individual susceptibility to irritation at the time of patch testing. Previous studies indicated that irritant SLS reactivity may be related to individual factors such as age and sex. As these factors are, in turn, among the important predictors of contact allergy to many allergens, e.g. summarized in the 'MOAHLFA index', the impact of the MOAHLFA factors on irritant SLS patch test reactivity, and thus a potential for confounding, was assessed in the 5971 participating patients. As a result of 2 logistic regression analyses with an irritant reaction to 0.25% and 0.5% SLS, respectively, as outcome, male sex was identified as a relatively weak but significant risk factor (OR 1.38), while age 40 years or older was an even weaker risk factor (OR 1.22 and 1.15, respectively). Upon detailed analysis, no clear age gradient could, however, be identified. 1-day exposure time almost halved the odds of an irritant SLS reaction. In conclusion, this type of SLS patch test can be regarded as robust, indicating individual irritability relatively independent from the individual factors analysed here.     

Results of routine patch testing with corticosteroid series in 2073 patients

The patch test results of 61 patients allergic to at least 1 corticosteroid molecule are presented. These contact allergies were detected by testing with several corticosteroids included in our standard patch test series between February 1988 and December 1990. Whenever possible, further investigations were conducted by means of a more complete corticosteroid series. We found corticosteroids to be the 7th most frequent allergen, positive results being obtained in 2.9% of all patients referred to our contact dermatitis unit. In this series, budesonide was the most common allergen and often gave simultaneous reactions with other corticosteroids.     

The effect of topically applied corticosteroid on irritant and allergic patch test reactions

The purpose of the study was to assess the effect of topical corticosteroid on the patch test response in patients with known positive allergens and also to study any effect on the irritant response. In Study 1, 10 patients with known positive allergens had their backs pre-treated 2× daily for 3 days with either betamethasone dipropionate 0.5% or the equivalent ointment base. On day 4, previous known allergens and dilutions of sodium lauryl sulfate (5% and 10%) as an irritant were applied to each side of the back. In Study 2 (4 patients), a 1:4 dilution of betamethasone dipropionate was substituted for the full-strength preparation. Betamethasone dipropionate 0.05% caused total or partial suppression of the allergic reaction in 8 of in eases. The 1:4 dilution caused partial suppression in 3 cases. The irritant reaction was totally suppressed by betamethasone dipropionate in 1 of 10 cases and partially suppressed in 7 of 10. The 1:4 dilution decreased the intensity of the irritant reaction in 3 of 4 cases. The relevance of these results to clinical practice is discussed.