Pre-treatment of nickel test areas with sodium lauryl sulfate detects nickel sensitivity in subjects reacting negatively to routinely performed patch tests

A fair % of patients with a clinical history of nickel allergy show negative patch test results. To improve the response rate to NiSO₄ 5% pet, patch tests, a testing procedure utilizing pre-treatment of I he lest area by a 24-h application of sodium lauryl sulfate (SLS) was introduced 46 women with a clinical history of nickel sensitivity who exhibited negative reactions to nickel sulfate 5% pet, patch tests. were studied, Patients underwent d patch tests on adjacent sites on the volar surface of the forcarms. 4 patch tests were performed with a 72-h application of 40 mg nickel sulfate 5% pet. While I of these patch tests served as control. 3 test areas underwent 24-h pretreatment with 40 μl SLS. 1 with 0.1% and 2 with 0.5% solution. To evaluate differences in the reactivity to SLS plus nickel sulfate related to the site on the forearm, 0.5% SLS pre-treatment was performed both on a proximal and on a distal lest site. At the 72-h evaluation. 19 subjects out of 46 showed positive reaction to nickel sulfate 5%. At skin sites pre-t railed with SLS. Whereas 23 patients reacted positively at 0.5% SLS pre-treated ureas. Echographic values of skin thickness and of hypo-echogeme dermal areas al positive pre-treated nickel lest. Next higher than al control Jest areas, confirming the clinical evidence of an increased response to NiSO₄ after SLS pre-treatment. The inflammatory reaction, is evaluated clinically and echographically, was much higher al distal skin areas (0.l% SLS and distal (0.5%.) SLS than at proximal 0.5% SLS ones.     

HLA class II restriction specificity for nickel-reactive T lymphocytes

Nickel-specific T cells were primed in vitro and restimulated with nickel in combination with autologous or allogeneic antigen-presenting cells. We have previously shown that not only DR, but also DQ molecules may take part in this process. To investigate this phenomenon further we applied recently available knowledge based on studies using specific cDNA probes and Restriction Fragment Length Polymorphism (RFLP), which has revealed a new level of DQ polymorphism, to search for a correlation of this polymorphism in the function of nickel-reactive T lymphocytes. We found that DQ, and presumably also DR, may restrict the proliferative response to nickel. The capacity of various antigen-presenting cells to cause restimulation correlated well, though not completely, with the specificity DQw1. RFLP splits of DQw1 did not yield any additional information on restriction specificity. Experiments using anti DR, DQ and DP monoclonal antibodies were performed, showing similar blocking capacity in all three antibodies. Work with cloned T cells is in progress to obtain more clearcut results concerning the HLA class II restriction of the proliferative T lymphocyte response to nickel.     

A placebo controlled observer blind immunocytochemical and histologic study of epithelium adjacent to anogenital warts in patients treated with systemic interferon alpha in combination with cryotherapy or cryotherapy alone.

OBJECTIVE--To examine biopsy specimens of tissue immediately adjacent to anogenital (AG) warts which had been treated with either cryotherapy plus subcutaneous interferon (IFN) alpha 2a or cryotherapy alone, for histological features of (a) human papilloma virus (HPV) infection (b) localised cellular immune responses, to further characterise any cellular immune infiltrates with tissue immunocytochemistry, and to relate any histological, immunocytochemical findings to the treatment response of nearby AG warts. DESIGN--A randomised placebo controlled observer blind study. SETTING--Genitourinary Medicine clinic, Department of Immunopathology, Royal Victoria Hospital, Belfast, N. Ireland. SUBJECTS--Thirty patients with AG warts; 16 treated with IFN alpha 2a plus cryotherapy, and 14 treated with cryotherapy alone. OUTCOME MEASURES--(1) Light microscopic features associated with HPV infection and local cellular immune responses. (2) Indirect immunofluorescence detection of the following cell surface markers: HLA DR, alpha one antitrypsin, CD1, CD3, CD4, CD8, CD22. (3) Clinical response of AG warts to treatment. RESULTS--In pre-treatment biopsies only non specific indicators of HPV infection (acanthosis, 29/30 biopsies, and hyperkeratosis, 7/30 biopsies) were seen on light microscopy. Mononuclear cells were seen both throughout the upper dermis and centred around dermal blood vessels in 19/30 (63.3%) biopsies, and infiltrating into the epidermis in 12/30 (40%) biopsies. On indirect immunofluorescence CD3, CD8, CD4 antigen was detected on the surface of cells throughout the upper dermis in 24/29 (82.7%), 15/29 (51.7%), and 3/29 (10.3%), of biopsy specimens respectively. CD3 antigen, CD8 antigen and CD4 antigen was detected on the surface of cells infiltrating into the epidermis in 18/29 (62%), 7/29 (24.1%), and 6/29 (20.7%) of biopsy specimens respectively. CD1 antigen was seen on the surface of dendritic cells throughout the epidermis in all specimens; CD1 positive cells infiltrated into the upper dermis in 5/29 (17.2%). HLA DR was detected on the surface of dendritic cells throughout the epidermis in 22/29 (75.9%) of specimens, and on the surface of cells scattered both diffusely throughout the upper dermis and centred around dermal blood vessels in all specimens. Alpha one antitrypsin (A1AT) antigen was seen on the surface of cells in the upper dermis in 6/29 (20.7%) of biopsy specimens; no cells expressing CD22 surface antigen were seen. The nature of this local cellular immune response was not altered by treatment of nearby warts with either cryotherapy alone or cryotherapy plus systemic IFN alpha 2a, or related to the therapeutic outcome of these warts. CONCLUSIONS--(1) No convincing histological evidence of HPV infection was seen in epithelium surrounding AG warts. (2) A predominantly T cell-mediated immune response (the target of which is uncertain) was seen in this perilesional epithelium. (3) In the dosage regimens used in this study, treatment of AG warts with either systemic IFN alpha 2a plus cryotherapy or cryotherapy alone did not appear to augment localised cellular immune responses (against any presumed subclinical HPV infection) in epithelium surrounding AG warts.     

Serum and urine nickel in nickel-sensitized women: effects of oral challenge with the metal

15 women with a positive patch test only to nickel (Ni) and without atopy and 10 control women were selected for the study. Blood and urine specimens were collected with a standard procedure either before (at 8 a.m.) or 4 and 24 h after the ingestion of 10 mg of Ni (as Ni sulfate). 7 of the Ni-sensitized patients showed a flare-up of eczema and/or urticaria during the test, while the other women were non-symptomatic. Serum and urine Ni of controls and Ni-sensitized women did not significantly differ. Serum and urine Ni levels determined before the oral Ni challenge were in the range of reference values recently reported by other authors (0.2–2.0 μg/l of serum or urine). Ni was greatly augmented in urine and serum 4 h after the challenge (25th–75th percentiles: 43–264 μg/l urine Ni and 15–52 μg/l serum Ni). 24 h after Ni ingestion, urine Ni was 41–153 μg/l and serum Ni 4–17 μg/l. Our study confirms a previous investigation showing similar levels of serum and urine Ni following ingestion of the metal in control and Ni-sensitized women without atopy.     

Long-lasting allergic patch test reactions: a study of patients with positive standard patch tests

The purpose of this study was to determine the duration of patch test reactions and the frequency of long-lasting allergic patch test reactions (LLAPTR), and to identify the possible factors related to the development of the LLAPTR. For this purpose, a group of 263 patients positive to 1 or more allergens in the GIRDCA standard series was recruited. Readings were made for each patient 2 and 3 days after patch test application and continued every 2nd and 3rd day until the disappearance of all palpable erythema. The % of LLAPTR out of the total of reactions was high: 17.9%). Kathon CG was the hapten that caused LLAPTR most frequently, with 16 cases, a frequency of 76.1%), and a mean duration of the patch test reactions of 25.4 days. Risk factors investigated were age, sex, atopy, intensity of the patch test reaction and sensitivity to some allergens with the greatest number of positive patch tests. The relative importance of each risk factor was calculated by multivariate stepwise logistic regression analysis. It was found that a Kathon CG sensitivity was the most important risk factor for LLAPTR. 2nd was atopy, followed by strong patch test reaction. Rejected risk factors were sex, age and sensitivity to nickel sulfate, potassium dichromate, Disperse Blue 124, fragrance mix and p-phenylenediamine.     

Inhibition of in vitro nickel sulfate reaction by anti-HLA-D/DR antisera. Lack of demonstrable suppressor cells in peripheral blood in nickel unresponsiveness in man

A nickel sulfate induced lymphocyte blast transformation reaction in vitro was specifically inhibited by anti-HLA-D/DR antisera, which indicates the requirement of HLA-D/DR antigens in cellular cooperation. Macrophages are effective antigen presenting cells in the in vitro nickel reaction and this step could be the site of an HLA-antigen function in the recognition of "self." It was shown that macrophages of an HLA identical, healthy sibling could offer proper "help" to macrophage-depleted lymphocytes of the nickel allergic subject in evoking a nickel reaction. Thus, in this respect, the function of macrophages in nickel allergy is not different from that in a nickel-unresponsive state. The nickel unresponsiveness in healthy subjects is probably not due to specific suppressor cells because HLA identical lymphocytes from the healthy siblings could not suppress the nickel induced blast transformation of the nickel allergic siblings. This suggests that a deletion of sensitized clones in the periphery is the more probable mechanism of unresponsiveness in healthy subjects.     

Reactivity to patch tests with nickel sulfate and fragrance mix in infants

The pattern of patch test reactivity to nickel sulfate and fragrance mix was studied with respect to patch test performance, reproducibility and clinical relevance in a population of unselected infants followed prospectively from birth to 18 months of age. TRUE Test™ patches with nickel sulfate in 3 concentrations, 200, 66 and 22 µg/cm², and fragrance mix 430 µg/cm² were used. A likely case of nickel sensitivity was defined as a reproducible positive reaction with at least homogeneous erythema and palpable infiltration occurring at least 2× and present at both the 12 and 18 months follow-up. 543 infants (268 girls and 275 boys) were tested at least 1×, 304 were tested at both 12 and 18 months. The prevalence of a reproducible positive reaction to nickel was 8.6% (20 girls and 6 boys). A transient positive reaction was observed in 111 children. Clinical relevance of nickel sensitivity was found in only 1 child. No reproducible positive reaction to fragrance mix was found. The high proportion of transient patch test reactivity to nickel sulfate 200 µg/cm² indicates that this standard concentration used for adults cannot be applied to infants. The interpretation of a single positive nickel patch test in infants must be assessed with caution and it is probably of non-specific or irritant nature.     

Influence of dietary factors,age and nickel contact dermatitis on nickel excretion

Background. Nickel is a frequently detected cause of allergic contact dermatitis. Ingestion of nickel may lead to flares of nickel contact dermatitis. Methods. We examined nickel excretion in the urine of 164 female patients with and without nickel contact dermatitis. The associations between age, atopic dermatitis, nickel contact dermatitis and nickel exposure through nutrition (e.g. dietary supplements) and by patch tests were investigated prospectively. Nickel was measured with atomic absorption spectrometry with two different standardized methods. Results. A nickel detection limit of 0.2 µg/l was exceeded by all samples. The 95th percentiles of urine nickel concentration were 3.77 µg/l (age 18–30 years) and 3.98 µg/l (age 31–46 years). Bivariate analyses pointed to significantly increased nickel excretion with increasing age, ingestion of dietary supplements, drinking of stagnant tap water, and consumption of nickel‐rich food. In the multivariate analysis, age and dietary supplements remained significant predictors of high nickel excretion. A non‐significant increase in the median concentration of nickel was observed after the administration of conventional nickel patch tests. Patients with atopic eczema showed urine nickel concentrations similar to those in non‐atopic controls. Conclusions. The 95th percentile of nickel excretion in our study population markedly exceeded the actual reference value of 3 µg/l. Age and consumption of dietary supplements are the most important predictors. The use of stagnant tap water and consumption of nickel‐rich food contribute to the total load. These factors should be explicitly mentioned when allergic patients on a low‐nickel diet are counselled. In contrast, existing nickel contact sensitization was not more frequent in subjects with higher nickel excretion. Nickel patch testing may cause transient minor systemic nickel exposure. The findings of this study extend our understanding and management of factors associated with nickel allergy.     

A comparative serological and molecular study of linear IgA disease and dermatitis herpetiformis

The class I and class II HLA serologically defined antigens and DQ alpha and DX alpha restriction fragment length polymorphism (RFLP) in 23 patients with linear IgA disease (LAD) were determined and their frequencies compared with those in a group of patients with dermatitis herpetiformis (DH) and healthy controls. In LAD there was a significant increase in HLA-B8 and DR3 and a larger increase in the DQw1-DR2/DRw6 related DQ alpha 6.2 kb and 6.8 kb RFLP. In DH there was a significantly increased frequency of HLA-A1, B8, DR3, and DQw2 with a concomitant increase in the DR3-DQw2 related DQ alpha 4.6 kb RFLP. The difference in DR3 frequencies and the increased frequency of DQw1 rather than DQw2 in LAD indicates that different susceptibility genes operate in the two diseases.     

Permeation of nickel through human skin in vitro—effect of vehicles

The effect of the vehicle on the permeation rate of nickel ions through excised human skin was evaluated. Different hydrogels were compared with the standard patch test in petrolatum. A hydroxypropyl methylcellulose gel seemed to be the most promising alternative to petrolatum. It gave high bioavailability of the nickel and had good film forming properties leaving the nickel spread across the skin surface as a thin film without microscopically detectable crystals. The content of nickel in the various skin layers after cutaneous application was determined, and nickel was found to accumulate in the epidermis, probably due to epidermal binding. A significant amount of nickel was found also in the dermis. Occlusion and application of higher nickel concentrations increased the transport rate and must be considered in patch testing using this hydrogel. We conclude that nickel permeation is highly dependent of the choice of vehicle and the vehicle should, therefore, be an important consideration in patch testing with nickel.     

Chromium, nickel and cobalt contents of some Australian cements

The total chromium, nickel and cobalt concentrations of 8 Australian Portland cements ranged from 49 to 99 μg/g, 5 to 54 μg/g and 1 to 13 μg/g, respectively. The water-soluble chromate concentrations of the cements ranged from 0.2 to 8.1 μg/g, and the sodium sulphate-extractable chromates from 1.4 to 9.7; μ g/g. Results for water-soluble nickel (0.2 μg/g) and cobalt (0.05 μg/g) indicate that the metals are present only as water-insoluble compounds. The significance of the various data is considered from a dermatological point of view. Cement extracts for the analysis of water-soluble hexavalent chromium (chromates) are stable for at least 12 days. The optimum extraction lime for hexavalent chromium in cement appears to be I h Almost 100% reduction of hexavalent chromium is possible after 1 h using 100x the stoichiometric value of iron (II) sulphate. The chromates can become gradually insolubilized when the solution from the water added is in direct contact with the cement, i.e., over a period of > 60 min to 7 days, even without the addition of iron (II) sulphate.     

HLA-A, -B and DR antigens in nickel sensitive females

The relationship between HLA antigens (A, B and DR) and nickel contact sensitivity was examined in a series of 26 female patients with unequivocal positive patch-test reactions to nickel. A comparison of patient antigen frequency versus Yorkshire Region HLA antigen figures showed an increased incidence of HLA-B35 in our patient population, (P < 0.01). The relative risk (RR) for the development of nickel sensitivity was reflected in the increased values for HLA-B35 and BW22 in our patients when compared with Yorkshire frequencies. We found no significant association between DR antigens and RR in our patients. The aetiological fraction (EF) showed no significant association between HLA antigens and nickel contact sensitivity.     

Increased expression of TRAIL and its death receptors DR4 and DR5 in plaque psoriasis

TNF-related apoptosis-inducing ligand (TRAIL) is recognized as an important regulator of immune responses during infections and various autoimmune-mediated pathologies. Its role in inflammatory dermatoses is largely unknown. We aimed to investigate the expression of TRAIL and its receptors DR4 and DR5 in psoriasis vulgaris. Immunohistochemistry for TRAIL, DR4 and DR5 was performed on samples of lesional (n = 10) and non-lesional (n = 10) skin of patients with plaque psoriasis and skin of healthy volunteers (n = 10). Expression of TRAIL and its receptors was further examined by means of double immunofluorescence staining and co-localization with CD4, CD8, CD11c, CD68, CD16 and CD56 markers. Immunohistochemical staining for TRAIL was significantly enhanced in psoriatic lesional as well as non-lesional epidermis compared to the epidermis of healthy skin. Lesional epidermis also showed increased immunoreactivity for DR5. In addition, expression of TRAIL and both of its receptors was significantly increased in the dermis of lesional skin. As evidenced by double immunofluorescence, TRAIL was readily expressed by most of the examined cells of the inflammatory infiltrate in psoriatic lesions. In contrast, the expression of DR4 was found mostly among CD4+ and CD8+ cells but was only nuclear, while DR5 showed cytoplasmic staining in rare CD16+, CD56+ and CD68+ cells. According to abundant in situ presence of TRAIL and its receptors in lesional psoriatic skin, it seems that this cytokine participates in the complex interplay between keratinocytes and cells of the dermal infiltrate and thus contributes to the inflammatory cycle in psoriasis vulgaris.     

Keratinocyte expression of MHC class II antigens in allergic sensitization and challenge reactions and in irritant contact dermatitis

Keratinocytes expressed major histocompatibility complex class II antigens during the development of irritant contact dermatitis, and during the induction of contact hypersensitivity, as well as in established allergic contact dermatitis. A battery of anti-class II monoclonal antibodies, some of which are specific for class II subregion products (DP, DQ, DR), was used in an immunohistochemical study of the sequential changes in the allergic challenge reactions to dinitrochlorobenzene (DNCB) and nickel, the irritant response to anthralin, and the induction of sensitization to DNCB. The induction of keratinocyte class II expression paralleled the influx of Leu-3a+ T cells into the skin and had occurred by 24 or 48 h in each type of reaction. Differential expression of class II subregion products on keratinocytes was noted: DR was the most frequently expressed molecule, followed by DP and DQ, although in the irritant response, DP expression was not observed. The importance of these observations can be decided only by functional studies.     

Dose-response testing with nickel sulphate using the TRUE test® in nickel-sensitive individuals. Multiple nickel sulphate patch-test reactions do not cause an "angry back"

Summary The aim of this study was to employ the TRUE test® assay to confirm the presence or absence of the 'angry back' phenomenon, i.e. that a strong positive patch-test reaction heightens adjustment patcht-est response. In addition, we wished to establish the dose-response relationship for nickel sulphate patch tests among nickel-sensitive patients. Seventy-two nickel-sensitive patients. 36 in Odense and 56 in Stockholm, were tested with a 10-step nickel sulphate dilution series (TRUE test® and two placebo patches. The position of the patches was rotated, to provide a balanced spatial distribution of the different concentrations. Readings were performed blind. The results were analysed by means of polynomial multiple-regression methods and a logistic dose–response model. Half the patients (38/72) had a threshold patch-test concentration for nickel sulphate in the range of 3.0—3 μg/cm². The 'angry back' phenomenon was not apparent in this study, as the spill-over effect was not statistically significant. Strong reactions to high concentrations of nickel sulphate did not enhance the response to adjacent lower concentrations of nickel sulphate.     

HLA-A, B, C and DR antigens in nickel contact sensitivity

The relationship between HLA antigens (A, B, C and DR) and nickel contact sensitivity was examined in 54 patients with contact allergy, as confirmed by an unequivocal positive patch-test reaction only to nickel. A control group was 320 healthy blood donors from the same geographical area as the patients. The HLA-A, B, C and DR antigens were typed using standard serological methods. HLA typing revealed a significant increase of HLA-DRw6 antigen in the patient group (corrected P less than 0.025) and the relative risk for patients with DRw6 to develop nickel sensitivity was 3.32.     

Iontophoresis of nickel elicits a delayed cutaneous response in sensitized individuals that is similar to an allergic patch test reaction

Wearing of patch test chambers for 1-2 days is uncomfortable for patients. Allergen application by iontophoresis avoids this, but it is unknown so far whether iontophoresis itself interferes with the delayed immune response. We compared the effects occurring 48 h after iontophoresis with distilled water, 0.9% NaCl, and 0.01 M NiSO4 in normal volunteers and in nickel-sensitized patients (total n=36). Visual assessment was performed and transepidermal water loss (TEWL), stratum corneum hydration, cutaneous blood flow, and immunohistopathology were determined. After iontophoresis with nickel sulfate, only individuals sensitized to nickel reacted with a positive clinical response, increase in cutaneous blood flow, decline in epidermal CD-1a-positive cells, increase in epidermal proliferation (Ki-67-positive cells), pronounced infiltration of cells positive for CD4, CD11, or CLA, and cellular activation (expression of ICAM1, HLA-DR). Iontophoresis with distilled water or saline did not result in such reactions in volunteers with or without nickel sensitization, and the latter also tolerated nickel iontophoresis without significant skin reactions. We conclude that the delayed cutaneous response to nickel induced via iontophoresis is specific and similar to a positive patch test reaction. Iontophoresis may therefore be considered as an alternative to patch testing.     

Hand dermatitis and allergic patch test reactions caused by nickel in electroplaters

A worksite survey was conducted in all 38 Finnish electroplating plants. All workers ( n =163) who worked with nickel plating (bath workers, hangers and solution makers) were interviewed with a questionnaire about symptoms of nickel dermatitis, hand dermatitis, and about protective measures, atopy, etc. Patch testing with nickel sulfate was done with the TRUE Test^TM method. All the workers, 94 men and 69 women, answered the questionnaire. The mean age of women was 41.1 years, and of men 43.1 years, respectively. Men had longer occupational exposure to nickel (14 years) than women (10 years). Most workers used protective gloves. 35% of women and 30% of men reported present or past hand dermatosis. 19% reported a history of atopic dermatitis. 15% of women ( n = 8) and 4% ( n = 2) of men had an allergic patch test reaction to nickel sulfate. 70% of those with an allergic patch test reaction to nickel reported past or present hand eczema. The prevalence of nickel allergy among the electroplaters was similar to that of patients in patch test clinics in Finland. An allergic patch test reaction to nickel sulfate does not necessarily oblige an electroplater to change jobs.     

Comparative in situ topoproteome analysis reveals differences in patch test‐induced eczema: cytotoxicity‐dominated nickel versus pleiotrope pollen reaction

Please cite this paper as: Comparative in situ topoproteome analysis reveals differences in patch test‐induced eczema: cytotoxicity‐dominated nickel versus pleiotrope pollen reaction. Experimental Dermatology 2010; 19: 511–517. Abstract: A subgroup of patients with atopic eczema develops acute eczematous reactions to type I allergy‐inducing agents such as pollen that clinically resemble type IV allergies induced by haptens like metal ions. To clarify the underlying immunologic mechanisms, this study was designed to map the inflammatory in situ topoproteome of eczematous responses to grass/birch pollen and nickel by using atopy patch test (APT) and nickel patch test (NPT) as an appropriate clinical model, respectively. Biopsies from NPT (n = 6) and APT (n = 6) with positive reactions at 72 h were analysed by multiple epitope ligand cartography (MELC), which enabled to investigate coexpression of 49 different epitopes immunohistochemically in a single given tissue section. Colocalisation of IgE and FcεRI was investigated by confocal microscopy. Compared with APT responses, NPT reactions were dominated by cytotoxic TIA‐1 + and CD8 + T cells. In contrast, the immune response in APT reactions appeared more pleiotrope – as detected by colocalisation analysis. Multiple combinatorial molecular phenotype (CMP) motifs containing naive, early maturation and memory T cell (CD45RA, CD7, CD44, CD45R0), and general activation markers (CLA, HLA‐DR, CD13, CD29, CD58, CD71, CD138) were significantly higher expressed in APT when compared with NPT reactions. APT response was confirmed to be accompanied by IgE bound to FcεRI. In summary, our results demonstrate that the NPT reaction is clearly dominated by cytotoxic events, while the APT reaction to pollen grains is more heterogeneous and elicits a combined humoral and cellular immune reaction.     

Patch testing with nickel sulfate: comparison between 2 nickel sulfate preparations and 2 different test sites on the back

Among patients routinely undergoing patch testing for suspected allergic contact dermatitis (ACD), nickel is the most frequently sensitizing hapten, with a clear predominance in the female population. However, some patients who report the appearance of dermatitis upon exposure to metal objects show negative patch test results to a nickel sulfate 5% pet. application. In some cases, a positive response to nickel can be observed simply by repeating the patch test. The objective of our study was to assess if, during routine patch testing, positive responses to nickel sulfate are missed owing to contingent problems, referring to application site, patch test execution or variations in skin reactivity. To this end, we applied 2 different patch test materials containing nickel sulfate 5% pet. to 3040 consecutive patients, undergoing patch testing for suspected allergic contact dermatitis, during the same session. The rôle of the test site was also investigated by applying the preparation on 2 different sites of the back in 30 patients. Of the whole, 612 patients (20%) showed positive patch test responses. The 2 nickel materials were almost equivalent: 78% of nickel-sensitive patients had positive reactions to both, whereas 11% showed a positive response to 1 preparation alone. No variations in patch test responses in relation to application site were observed. Our data show that false-negative patch test responses to nickel are frequent. The use of 2 different preparations during the same patch test session increases the response rate by 10%.