Positive Patch Test Reactions Research Articles

Contact allergy to hair cosmetic allergens in Thailand

Hair cosmetics such as hair dyes, bleaching, waving, and cleansing products are composed of numerous chemical ingredients. Allergic reactions to these contact allergens, other than p-phenylenediamine, are rarely reported. To study the incidence of patch test reactions to hair cosmetic allergens and identify the factors associated with hair cosmetic allergy in Thailand. We retrospectively reviewed the case records of patients who underwent patch testing from 2009 to 2018. Patients with at least one positive patch test reaction to a potential contact allergen associated with hair cosmetic ingredients were studied. Overall, 2842 patients were patch tested. Of the hair cosmetic allergen categories, preservatives had the highest rate of positive reactions, followed by surfactants and hair dyes. Perming agents were less problematic in comparison. The hands, head, and neck were the predominately affected sites of allergic reactions to hair cosmetic ingredients. Preservatives, surfactants, and hair dyes are important contact allergens, whereas perming agents are less likely to cause allergic reactions. Hair cosmetic ingredients are regulated by national agencies, which influences their extent of exposure and rates of contact allergies. Further continuous observation of hair cosmetic allergy is needed to provide the best patient care.

Thimerosal induces skin pseudo-allergic reaction via Mas-related G-protein coupled receptor B2

BackgroundThimerosal has been used as a preservative in many products which may cause contact dermatitis. It is the second most common allergen in positive patch test reactions, though being a clinical irrelevant allergen. Thimerosal-induced contact dermatitis is generally considered to be a delayed-type hypersensitivity reaction, but it is difficult to explain the fact that most patients develop an allergic reaction upon first encounter with thimerosal. Recent studies have demonstrated the association between Mas-related G protein coupled receptor X2 (MRGPRX2) and pseudo-allergic reactions which occur at the first contact with stimulation. This suggests the possibility that thimerosal may cause contact dermatitis via MRGPRX2 mediated mechanism. ObjectivesTo investigate the role of Mas-related G-protein coupled receptor B2 (MrgprB2)/MRGPRX2 in contact dermatitis induced by thimerosal. MethodsThimerosal induced pseudo-allergic reactions via MrgprB2/ MRGPRX2 were investigated using a novel skin pseudo-allergic reaction mouse model, footpad swelling and extravasation assays in vivo and mast cell degranulation assay in vitro. ResultsThimerosal induced contact dermatitis in dorsal skin and footpad swelling in wild-type mice, but had no significant effect in MrgprB2-knockout mice. Thimerosal-induced dermatitis is characterized by infiltration of inflammatory cells and elevation of serum histamine and inflammatory cytokines, rather than elevation of serum IgE level. Thimerosal increased the intracellular Ca2+ concentration in HEK293 cells overexpressing MrgprB2/MRGPRX2. Downregulation of MRGPRX2 resulted in the reduced degranulation of LAD2 human mast cells. ConclusionsMrgprB2 mediates thimerosal-induced mast cell degranulation and pseudo-allergic reaction in mice. MRGPRX2 may be a key contributor to human contact dermatitis.

Unexpected positive patch test reactions to sesquiterpene lactones in patients sensitized to the glucose sensor FreeStyle Libre

Most diabetic patients sensitized to FreeStyle Libre react to isobornyl acrylate (IBOA), with a considerable number of them also showing unexpected positive patch test reactions to sesquiterpene lactone (SL) mix (SLM) tested in the baseline series. To compile patch test results of subjects affected, and provide potential explanations for this association. Fifty-three Freestyle Libre-allergic patients were patch tested with IBOA and/or SLM, and several were also patch tested with the components of SLM. Chromatographic analyses were performed on the glucose sensor, IBOA, and the components of SLM. Thirty-three patients reacted positively to the components of SLM, and 11 of 27 patients reacted positively to alantolactone, in particular. Gas chromatography-mass spectrometry (GC-MS) analyses did not detect these chemicals in the different parts of the glucose sensor, or in IBOA. Significant co-sensitizations between SLs on the one hand and the glucose sensor FreeStyle Libre and/or isobornyl acrylate on the other hand exist, without evidence of the presence of SLs via GC-MS analysis. Cross-reactions between them seem improbable. As a possible hypothesis, a common precursor for both, such as camphene, may exist.

The impact of ultraviolet exposure on patch testing in clinical practice: a case-control study.

Current guidelines suggest waiting a full 6weeks between ultraviolet (UV) exposure and patch testing owing to the localized and generalized cutaneous immunosuppression it induces, yet there is a dearth of evidence as to the duration of this immunosuppression. To determine whether there are any significant differences in the rates of positive patch-test reactions between patients who had received a significant exposure to UV within the previous 6weeks, and similar patients who had not received such an exposure. Rates of positive patch-test reactions were compared between patients undergoing patch testing for generalized eczema who had completed a course of phototherapy within the preceding 6weeks, and matched controls who had not. Patients were matched for sex, age and naivety to systemic therapy. Of the 22 patients who had received phototherapy, 7 exhibited at least 1 positive reaction, compared with 6 of the 22 controls; this result was not significant (P>0.05). The cutaneous immunosuppression induced by UV exposure appears to be fully resolved within <6weeks. This suggests it may therefore not be necessary in all cases to wait the full 6weeks following significant UV exposure before undertaking patch testing.

New positive patch test reactions on day 7-The additional value of the day 7 patch test reading.

BackgroundNot performing a day (D) 7 patch test reading might result in positive patch test reactions being missed.ObjectivesTo investigate the added value of the D7 patch test reading for individual allergens, and to identify patient characteristics and allergen groups associated with new positive D7 reactions.MethodsData from patients patch tested between 2008 and 2018 with the extended European baseline series were analysed. Patch test readings were performed on D3 and D7. Positive reactions were categorized into positive on D3 or new positive on D7.ResultsA total of 3292 patients were consecutively patch tested with at least 43 allergens of the TRUE Test panels 1 and 2 supplemented with investigator‐loaded allergens. In total, 447 (13.6%) patients showed new positive D7 reactions. In univariable regression analysis, age between 18 and 30 years showed a negative association with new positive D7 reactions. Significantly more D7 positive reactions were seen for topicals (odds ratio [OR] 2.60, 95% confidence interval [CI]: 1.92‐3.51) and corticosteroids (OR 1.87, 95%CI: 1.09‐3.21). No associations were found between sex, atopic dermatitis and occupational dermatitis and a new positive D7 reaction.ConclusionA D7 reading to identify new positive patch test reactions is of added value, especially for topicals and corticosteroids.

Causative exposures and temporal development of cobalt allergy in Denmark between 2002 and 2017.

Cobalt contact allergy is common, but clinical relevance is often difficult to determine. To examine the aetiology, prevalence and clinical characteristics of cobalt-allergic patients who were patch tested between 2002 and 2017 at the Department of Dermatology and Allergy, Herlev-Gentofte Hospital. Patch test data, along with patient characteristics and causative exposures, from all adult dermatitis patients seen and tested between 2002 and 2017 were analysed. Associations were tested with the χ 2 test and logistic regression. A total of 13 475 adults aged 18 to 99 years were patch tested. The overall prevalence of cobalt allergy and the prevalence of isolated cobalt allergy were 3.3% and 1.5%, respectively. The prevalence of isolated cobalt allergy decreased from 2.4% in 2006 to 2009 to 1.1% in 2014 to 2017 (Ptrend = 0.00003). Leather exposure as a relevant cause of allergic cobalt dermatitis increased from 3.7% in 2002 to 2009 to 8.3% in 2010 to 2017 (P = 0.04). The current clinical relevance of positive patch test reactions, that is, a positive reaction to cobalt combined with a history of current skin exposure to a source of cobalt, was 20.1%. We conclude that cobalt allergy is relatively common, but causative exposures are largely unknown, and the proportion of positive patch test reactions with clinical relevance is low. It is therefore currently unclear how we can better protect consumers and workers from cobalt exposure.

Sensitization potential and potency of terpene hydroperoxides in the cocultured activation test method.

Positive patch test reactions to mixtures of oxidized terpenes containing allergenic hydroperoxides are frequently reported. However, human sensitization data for these hydroperoxides are not available. To analyse and evaluate the human sensitization potential and potency of hydroperoxides in vitro by using human cells. Limonene-1-hydroperoxide, limonene-2-hydroperoxide, citronellol-7-hydroperoxide, cumene hydroperoxide, 1-(1-hydroperoxy-1-methylethyl)cyclohexene and mixtures of citronellol hydroperoxides (isomers at positions 6 and 7) and linalool hydroperoxides (isomers at positions 6 and 7) were studied. All compounds were synthesized except for cumene hydroperoxide, which was commercially available. Their potential and potency to activate dendritic cells (DCs) was evaluated by measuring the upregulation of CD86 and CD54 on THP-1 cells upon exposure in the cocultured activation test (COCAT) consisting of HaCaT cells (human keratinocyte cell line) and THP-1 monocytes (as a surrogate for DCs). Hydroperoxides upregulated CD86 and/or CD54 on cocultured THP-1 cells in a concentration-dependent manner. The results are comparable with their sensitization potency ranking in predictive animal models. For the first time, the human sensitization potential and potency of several hydroperoxides were determined by the use of human cells and the COCAT method.

Screening for Gold Sensitization in Consecutive Eczema Patients: Prevalence, Relevance, and Sources of Exposure.

Since the 1990s, gold has been recognized as an important contact allergen. Based on our results with gold sodium thiosulfate (GST) in the TRUE Test patch test system in the baseline series, the aims of the study were to evaluate baseline testing with gold salts worldwide and to discuss relevance. Patients with positive patch test reactions to GST were questioned on exposure at day 7 reading. In a 1-year period, 89 (18.5%) of 480 patients tested positive to GST, making this the most frequent contact allergy. The 89 patients comprised 18 males and 71 females. The reaction was considered relevant in 21%; this is a minimum figure because 2 patients were withdrawn because of unknown relevance and because clinical features suggestive of gold contact allergy at distant sites, such as the face, were not taken into account. Altogether, 88% had been exposed. Worldwide, the prevalence of gold sensitization ranges between 0.78% and 30.7%, and relevance, in larger studies, has been between 15% and 20% of patients. The use of earrings and the presence of dental gold were important sources of exposure. Because it may be difficult to diagnose gold allergy, screening may be recommended when history taken suggests gold exposure.

Filaggrin gene loss-of-function mutations constitute a factor in patients with multiple contact allergies.

Polysensitivity is defined as three or more positive patch test reactions. The role of filaggrin gene (FLG) loss-of-function mutations in patients with polysensitivity has not been studied when barrier bypass and possible preceding barrier damage have been excluded. To determine whether FLG loss of function mutations play a role in patients with multiple contact sensitivities when barrier bypass is excluded. One hundred and sixty-nine patients with three or more, non-cross-reacting, positive patch test reactions were prospectively enrolled in this study. Exclusion criteria were a history of hand dermatitis, nickel and metal implants, and stasis dermatitis. Subjects were patch tested with the North American extended patch test series, and with other relevant haptens. DNA was obtained and sequenced for the following FLG loss-of-function mutations: R501X, 2282del4, R2447X, and S3247X. One hundred and sixty-five patients were genotyped for the four FLG mutations. There was a significant association between R501X mutation and polysensitivity. For the other three tested mutations, there were no significant associations with polysensitivity. When all mutations were combined, there was a significant association between loss-of-function FLG mutations and polysensitivity in patients with a history of atopic dermatitis. When skin barrier bypass is excluded, there is a significant association between polysensitivity and FLG loss-of-function mutations.

Myroxylon pereirae resin (balsam of Peru) - A critical review of the literature and assessment of the significance of positive patch test reactions and the usefulness of restrictive diets.

In this article, contact allergy to Myroxylon pereirae resin (MP) (balsam of Peru) is reviewed. The topics presented include the uses, the chemical composition, the frequency of sensitization, the relevance of positive reactions, the MP-containing products causing allergic contact dermatitis, co-reactivity with other fragrance and non-fragrance materials, the sensitizers, the usefulness of MP as a "marker" of fragrance allergy, and the effectiveness of, and indications for, "balsam-restrictive" diets. Sensitization to MP occurs in 4% to 8% of patients routinely tested for suspected contact dermatitis. There are few adequate data on relevance. Topical pharmaceuticals were formerly, but are not today, important sources of sensitization. Cosmetics and foods or drinks are hardly ever products responsible for sensitization to MP. Positive patch test reactions in the large majority probably result from previous sensitization to MP constituents because of their presence in fragrances and fragranced products, MP thereby acting as marker (or "indicator") of fragrance allergy. However, fragrance mix I is a more sensitive marker, and the added diagnostic value of testing with MP is unknown. The allergenic ingredients of MP include isoeugenol, eugenol and cinnamyl alcohol, but there are other-largely unknown-chemicals that are responsible for contact allergy. Suggestions are given for further research to address questions thus far unanswered and to improve patient care.

Exploring the Incidence, Implications, and Relevance of Metal Allergy to Orthopaedic Surgeons.

Introduction:Allergic reactions to metal implants are increasingly recognized, but its relevance to the orthopaedic surgeon remains unclear. We evaluate the prevalence of metal allergies in a subset of the population and review the significance through a survey of the current literature.Methods:Preoperative and postoperative patients referred for metal allergy testing were divided into two groups; those with a history of dermatitis and those without. Patients with a history of dermatitis were offered skin patch testing that included the North American Contact Dermatitis core allergen panels in addition to our metal screening series. Patients without dermatitis were tested to the more limited patch testing metal screening series. Some patients with dermatitis opted for the more limited screening, whereas some patients without dermatitis underwent more extensive testing at their request or at the request of the referring clinician. Patch tests were evaluated at 2 and 4 days after placement.Results:Hundred patients were referred for metal allergy testing, 46 of whom were for reasons related to planned orthopaedic surgery. Of those tested, 60 patients had a history of dermatitis and 40 did not. Some patients were nonreactive to all tested allergens, whereas others demonstrated one or more positive skin patch test reactions. The number of positive reactions to each metal in patients with a history of dermatitis was the following: nickel 19, amalgam 10, palladium 10, copper 8, cobalt 5, mercury 5, tin 2, gold 1, titanium 1, and vanadium 1. The number of positive reactions to metals in patients without a history of dermatitis was the following: nickel 4, amalgam 5, palladium 4, mercury 4, cobalt 4, tin 2, copper 2, gold 1, vanadium 1, and molybdenum 1.Discussion:Metal allergy was common in the individuals referred for testing, with reactions to nickel and amalgam being the most commonly encountered. Some individuals experience more notable allergic reactions to implanted devices than others. Localized and generalized skin reactions have been reported, along with implant failure and loosening. Surgeons should be aware of the incidence of metal allergies and the potential consequences.

Exposure source for skin sensitizing hydroperoxides of limonene and linalool remains elusive: An analytical market surveillance

Positive patch test reactions of dermatological patients to oxidized samples of linalool and limonene are frequently reported. The sensitizing ingredients in the oxidation mixtures are hydroperoxides (HP). It is not clear whether fragranced consumer products are a relevant exposure source for HP. Analytical methodologies had been validated, allowing quantification of HP in different consumer products. The analytical approach was used to analyse 104 consumer products. Samples included aged and new samples from the same brand, products suspected by patients to elicit their symptoms and products containing essential oils. Only four samples contained >50 μg/g of at least one of the HP by the screening method. Confirmatory analysis by LC-MS methods indicated that levels are even below those observed by the conservative screening method. The samples retrieved from patch-test positive patients were below detection limit for all target analytes. This market surveillance indicates that concentrations of HP in consumer products and patient products are orders of magnitude below sensitizing doses in animal tests. No evidence for hydroperoxide accumulation in aged products or products used by patients was found. The nature and source of the inducing agent responsible for the frequent positive patch test reactions to oxidized terpenes remains elusive.

Diagnosing lanolin contact allergy with lanolin alcohol and Amerchol L101.

BackgroundThe prevalence of lanolin contact allergy in dermatitis patients varies from 1.2% to 6.9%. Different lanolin derivatives are used in patch testing.ObjectivesTo determine which combination of lanolin derivatives is most effective in patch testing for the diagnosis of lanolin contact allergy.MethodsA retrospective analysis of patients patch tested between 2016 and 2017 was performed. Patients were eligible if they had been tested with lanolin alcohol 30% pet., Amerchol L101 50% pet., and a supplementary series containing other lanolin derivatives. Lanolin alcohol and Amerchol L101 were tested in duplicate.ResultsOf 594 patients, 28.6% (95% confidence interval [CI]: 25.1%‐32.3%) had a positive patch test reaction to at least one lanolin derivative. Reactions to lanolin alcohol (14.7%, 95%CI: 11.3%‐18.2%) and Amerchol L101 (15.0%, 95%CI: 11.5%‐18.5%) were common in the routinely tested series. Reactions to other test preparations were significantly less frequent (P < 0.05). The addition of Amerchol L101 to lanolin alcohol significantly increased the number of positive cases (odds ratio 1.79, P < 0.001).ConclusionsThe combination of lanolin alcohol and Amerchol L101 is effective in patch testing for the diagnosis of lanolin contact allergy. Routinely testing with other lanolin derivatives may not be worthwhile, as it detects only a few additional patients.

Allergic contact dermatitis caused by topical ophthalmic medications: Keep an eye on it!

Allergic contact dermatitis (ACD) caused by topical ophthalmic medications is often overlooked. To study the demographic characteristics, lesion locations and associated medical conditions of the patients with ACD caused by ophthalmic drugs, and to identify the most common allergenic culprits, as well as trends in frequencies over the years. From January 1990 until December 2016, 16 065 patients were investigated in our clinic; all patients with a positive patch test reaction to an eye medication or its ingredient(s) having caused ACD were assessed. For each allergen identified, the number of positive test results as compared with the total number of those in the total population, as well as trends across three periods, namely 1990 to 1998, 1999 to 2007, and 2008 to 2016, were studied. One hundred and eighteen patients (0.7%) presented with positive patch test reactions to ingredients of and/or topical ophthalmic medications. Aminoglycoside antibiotics, followed by corticosteroids, as pharmacologically active ingredients, as well as wool alcohols, thiomersal, and benzalkonium chloride, as excipients, were the most frequent culprits. Chloramphenicol showed a decreasing trend of positive reactions over time, whereas reactions to tobramycin increased. ACD caused by eye medication is mainly attributable to active principles, but other excipient ingredients, beside the products "as is," should be tested as well.

Concomitant contact-allergic reactions to iodopropynyl butylcarbamate and iodine.

Iodopropynyl butylcarbamate (IPBC) is a broad-spectrum preservative for use in several product types, including cosmetics, in which its concentrations have been limited by EU legislation because of concerns related to its iodine content and release, and the risk of subsequent iodine overdose. To report on concomitant patch test reactions observed with iodine and IPBC in patients sensitized to iodine-containing antiseptics. Between 2012 and 2018, seven patients, six from Belgium and one from France, two suffering from acute dermatitis during surgical interventions, four from dermatitis caused by wound treatment, and one from occupational dermatitis, were shown to be sensitized to iodine and/or povidone-iodine (PVP-I), which was considered to be relevant for their dermatitis. All patients were coincidentally also patch tested with IPBC. All patients showed positive patch test reactions to several other allergens, including IPBC. No relevance could be detected for IPBC. We suspect that, notwithstanding the absence of firm evidence for IPBC being dehalogenated to produce free iodine in animals or in humans, the patch test reactions to IPBC in iodine-allergic subjects were possibly caused by free iodine released from this preservative agent, thus underlining the EU restrictions regarding the use of this preservative in cosmetics.

Variable impact of dupilumab on patch testing results and allergic contact dermatitis in adults with atopic dermatitis

Previous case reports and series suggested that dupilumab may be an effective treatment for allergic contact dermatitis (ACD). Little is known about the impact of dupilumab on patch test results and comorbid ACD in patients with atopic dermatitis (AD). Determine the impact of dupilumab on patch testing results and improvement of ACD in patients with AD. A retrospective study of patients with AD treated with dupilumab who underwent patch testing (n=7) or had concomitant ACD (n=6). In all, 7 patients with AD were patch tested while taking dupilumab; in all of these patients, at least 1 positive patch test reaction was observed, with a total of 25 different allergens having a reaction graded as 1+or stronger and few irritant reactions. In 1 patient, multiple previously positive relevant patch test results were not duplicated upon repeat patch testing. In the 6 patients with AD and concomitant ACD, dupilumab and allergen avoidance resulted in substantial or complete resolution of AD signs and symptoms but resolution of ACD in only 3 patients. However, 3 patients had at least 1 flare of ACD upon re-exposure to relevant allergens. Retrospective and uncontrolled study. Dupilumab had variable impact on patch testing results and resolution of comorbid ACD in adult patients with AD.

Twenty‐eight‐day follow‐up of patch test reactions to p‐phenylenediamine and p‐phenylenediamine dihydrochloride: A multicentre study on behalf of the European Environmental and Contact Dermatitis Research Group

There is an ongoing discussion on whether routinely patch testing with p-phenylenediamine (PPD) 1.0% pet. is safe, owing to the risk of patch test sensitization. Late-appearing patch test reactions may reflect patch test sensitization, but may also be attributable to a low degree of pre-existing sensitization. To follow the positive patch test reactions to PPD and its salt PPD dihydrochloride (PPD-DHC) in order to characterize reaction patterns concerning time and dose in PPD-sensitized individuals. Volunteers with previous reactions to PPD 1.0% were included and patch tested with PPD and PPD-DHC in equimolar dilution series. There were then seven follow-up visits over a period of 28 days. Twenty-six volunteers completed the study, of whom 23 of 26 (88%) reacted to PPD 1.0%, and 69% reacted to PPD 0.32%. Altogether, 42% and 27% reacted to the corresponding equimolar concentrations of PPD-DHC. After day 7, no new reactions were observed to any concentration tested, either of PPD or of PPD-DHC. No late-appearing reactions to PPD or PPD-DHC were observed at any dose. There is a risk of missing contact allergy when the dose is decreased.

Piroxicam-induced fixed drug eruption: Cross-reactivity with meloxicam.

Non-steroidal anti-inflammatory drugs constitute a main cause of fixed drug eruption (FDE). A few cases of piroxicam-induced FDE have been reported; however, the cross-reactivity among oxicams has rarely been evaluated. To describe a series of patients with piroxicam-induced FDE, mostly confirmed by a positive patch test reaction, in whom cross-reactivity to meloxicam was assessed. We included all cases of piroxicam-induced FDE diagnosed in the department of pharmacovigilance of Monastir. Patch tests for piroxicam and meloxicam were performed in the involved skin according to the European Network on Drug Allergy recommendations. Oral provocation tests (OPTs) were performed for patients with negative skin test results. Seven patients were included in this study. FDE was multiple for five patients and solitary for two. Bullous eruption was noticed in two cases. Lesional patch tests for piroxicam gave positive results in six patients. To assess cross-reactivity with meloxicam, this was patch tested. The test gave a positive result in only one patient. OPTs with meloxicam gave positive results in two patients with negative patch test results. Meloxicam is not a safe alternative for the treatment of piroxicam-induced FDE, and OPTs can be used to confirm tolerance before this drug is prescribed as a safer alternative.

Effect of Patch Testing on the Course of Allergic Contact Dermatitis and Prognostic Factors That Influence Outcomes.

Allergic contact dermatitis (ACD) has been shown to adversely affect the quality of life of patients. The aim of the study was to study the effect of patch test on the severity of dermatitis, the quality of life of patients, and the prognostic factors influencing the outcome. The study included 111 patients patch tested with the preliminary diagnosis of ACD. Patients with clinically relevant positive patch test reactions were included in the ACD group. All patients were assessed with the Investigator Global Assessment and the Dermatology Quality of Life Index before and 6 months after patch testing. At the sixth-month control, more significant regressions in the mean Investigator Global Assessment and Dermatology Quality of Life Index scores were noted in the ACD group. The allergens were correctly remembered by 75% of the patients. The improvement was more significant in patients with ACD who correctly remembered the allergens and made appropriate lifestyle changes. Multiple allergen positivity was identified as a poor prognostic factor. The effect of patch test on the prognosis of contact dermatitis depends not only on providing necessary information to patients but also on the number of positive reactions, patient's ability to recall the allergens, how much the avoidance was achieved, and patient-related factors such as sex.

European Surveillance System on Contact Allergies (ESSCA): Contact allergies in relation to body sites in patients with allergic contact dermatitis.

BackgroundAnalyses of the European Surveillance System on Contact Allergies (ESSCA) database have focused primarily on the prevalence of contact allergies to the European baseline series, both overall and in subgroups of patients. However, affected body sites have hitherto not been addressed.ObjectiveTo determine the prevalence of contact allergies for distinct body sites in patients with allergic contact dermatitis (ACD).MethodsAnalysis of data collected by the ESSCA (www.essca‐dc.org) in consecutively patch tested patients, from 2009 to 2014, in eight European countries was performed. Cases were selected on the basis of the presence of minimally one positive patch test reaction to the baseline series, and a final diagnosis of ACD attributed to only one body site.ResultsSix thousand two hundred and fifty‐five cases were analysed. The head and hand were the most common single sites that ACD was attributed to. Differences between countries were seen for several body sites. Nickel, fragrance mix I, cobalt and methylchloroisothiazolinone/methylisothiazolinone were the most frequent allergens reported for various body sites.ConclusionsDistinct allergen patterns per body site were observed. However, contact allergies were probably not always relevant for the dermatitis that patients presented with. The possibility of linking positive patch test reactions to relevance, along with affected body sites, should be a useful addition to patch test documentation systems.