Positive Patch Test Reactions Research Articles

Contact sensitization and self-reported eczema in Swedish painters with occupational exposure to isothiazolinones.

Due to an increasing occupational usage of isothiazolinone (IT)-containing preservatives, and their potential to cause skin sensitization and allergic contact dermatitis, that is, chronic disease, there is a need for more knowledge on how highly exposed workers are affected. The overall objective was to explore dermatological symptoms of potentially long-lasting or chronic character in Swedish painters. Building painters from western and southern Sweden were initially invited to perform a questionnaire on occurrence of skin symptoms. Participants with affirmative responses, and the right inclusion criteria, were further invited to patch testing with four different ITs: benzisothiazolinone (BIT), methylisothiazolinone, methylchloroisothiazolinone and octylisothiazolinone. There was a tendency towards higher occurrence of positive patch test reactions among the painters compared with occupationally unexposed registry patients; however, not statistically significant differences. BIT was the substance most frequently causing positive test results in both groups. The occurrence of adult-onset eczema was higher in painters than in the control group of electricians, and just shy of statistical significance concerning any of several skin locations (face/legs/arms/hands). Building painters present with positive patch test reactions to common paint preservatives (ITs), and they report adult-onset eczema more often than do less occupationally exposed groups.

2-Hydroxyethyl methacrylate (2-HEMA) sensitization, a global epidemic at its peak in Spain?

A global epidemic of allergic contact dermatitis to (meth)acrylates has been described in relation to the widespread use of manicure products. To evaluate the frequency of sensitization to 2-hydroxyethyl methacrylate (2-HEMA) among consecutively patch tested patients with eczema in Spain; the percentage of current relevance; the MOAHLFA index; and, the potential sources of exposure to (meth)acrylates. From January 2019 to December 2022, 2-HEMA 2% pet. was prospectively patch tested in 24 REIDAC (Spanish Allergic Contact Dermatitis Registry) centres. Six thousand one hundred thirty-four patients were consecutively patch tested with 2-HEMA 2% pet. 265/6134 (4.3%) were positive. Positive reactions of current relevance were identified to involve 184/265 (69%). The efficiency (number of patch tests needed to detect relevant positive patch test reactions) was 34 (6134/184). The variable 'occupational' was found to be significantly associated with a higher risk for relevant positive reactions to 2-HEMA (OR: 10.9; 95% CI: 8.1-14.9). (Meth)acrylate sensitization is a prevalent health issue in Spain. 2-HEMA 2% pet. has been identified to be a highly effective (meth)acrylate allergy marker in the GEIDAC baseline series. The responsible authorities should implement policies guaranteeing accurate labelling of industrial, medical, and consumer materials while ensuring the enforcement of said labelling through appropriate legal means.

Gene profiling in active dermatitis lesions strengthens the diagnosis of allergic contact dermatitis

BackgroundDistinguishing between allergic and non-allergic forms of Contact Dermatitis (CD) is challenging and requires investigations based on patch-testing. Early detection of allergy biomarkers in active CD lesions could refine and simplify the management of CD patients. ObjectiveTo characterize the molecular signatures of active CD lesions. MethodsWe studied the expression of 12 allergy biomarkers by qRT-PCR in active lesions of 38 CD patients. Allergic CD (ACD) was diagnosed based on patch-test (PT) results and exposure assessment. Molecular signatures of active lesions, as well as positive PT reactions, were compared with those of reference chemical allergens and irritants. Results19 of the 38 CD patients reacted positively upon patch-testing and exposure assessment confirmed ACD diagnosis for 17 of them. Gene profiling of active CD lesions revealed two distinct molecular patterns: patients harboring signatures similar to reference allergens (n=23) or irritants (n=15). Among the 23 patients with an “allergy signature”, we found the 17 patients with confirmed ACD, while no culprit allergen was identified for the 6 other patients. Interestingly, the 15 patients without biomarker induction had negative PT, suggesting that they developed non-allergic CD reactions. ConclusionMolecular signatures from active skin lesions may help to stratify CD patients and predict those suffering from allergic contact dermatitis.

Contact allergens in African countries: A review of published patch test studies

AbstractOnly few studies on contact allergy in African countries have been published. The aim of the present study was to provide an overview of the most common contact allergens identified by the use of patch tests in African countries based on a review of the existing literature. A total of twenty‐four publications from eight African countries were initially identified by search in PubMed. The abstracts and method sections were screened, and 15 studies in which patch tests were actually used to identify the allergen causing the allergic contact dermatitis (ACD) were finally selected. Nickel, cobalt, chromium, fragrance mix and p‐tert‐butylphenol‐formaldehyde resin were the dominating contact allergens responsible for 40%–90% of the positive patch test reactions. This study indicates that a targeted effort directed towards prevention, avoidance and regulation of reliably identified contact allergens could reduce the disease burden of ACD considerable in some African countries.

Prevalence of allergic contact dermatitis in children with and without atopic dermatitis: A multicenter retrospective case-control study.

As both allergic contact dermatitis and atopic dermatitis (AD) have similar clinical presentations and are characterized by spongiotic dermatitis on skin biopsy, many children with AD are not referred for patch testing and allergic contact dermatitis is underdiagnosed. To provide updated prevalence data of common contact allergens in children with and without AD. This is a retrospective case-control study using the Pediatric Allergic Contact Dermatitis Registry from 2018 to 2022. A total of 912 children were included (615 with AD and 297 without AD). Children with AD were more likely to have a longer history of dermatitis (4.1 vs 1.6years, P<.0001), have seen more providers (2.3 vs 2.1, P=.003), have greater than 1 positive patch test (PPT) result (P=.005), have a greater number of PPT results overall (2.3 vs 1.9, P=.012), and have a more generalized distribution of dermatitis (P=.001). PPT to bacitracin (P=.030), carba mix (P=.025), and cocamidopropyl betaine (P=.0007) were significantly increased in children with AD compared to those without AD. Technical variation between providers and potential for misclassification, selection, and recall biases. Children with AD are significantly more likely to have PPT reactions and should be referred for evaluation of allergic contact dermatitis and obtain patch testing.

More than just methylisothiazolinone: Retrospective analysis of patients with isothiazolinone allergy in North America, 2017-2020

Isothiazolinones are a common cause of allergic contact dermatitis. To examine the prevalence of positive patch test reactions to isothiazolinones from 2017-2020 and characterize isothiazolinone-allergic (Is+) patients compared with isothiazolinone nonallergic (Is-) patients. Retrospective cross-sectional analysis of 9028 patients patch tested to methylchloroisothiazolinone (MCI)/methylisothiazolinone (MI) 0.02% aqueous, MI 0.2% aqueous, benzisothiazolinone (BIT) 0.1% petrolatum, and/or octylisothiazolinone (OIT) 0.025% petrolatum. Prevalence, reaction strength, concurrent reactions, clinical relevance, and source of allergens were tabulated. In total, 21.9% (1976/9028) of patients had a positive reaction to 1 or more isothiazolinones. Positivity to MI was 14.4% (1296/9012), MCI/MI was 10.0% (903/9017), BIT was 8.6% (777/9018), and OIT was 05% (49/9028). Compared with Is-, Is+patients were more likely to have occupational skin disease (16.5% vs 10.3%, P <.001), primary hand dermatitis (30.2% vs 19.7%, P <.001), and be >40years (73.1% vs 61.9%, P<.001). Positive patch test reactions to >1 isothiazolinone occurred in 44.1% (871/1976) of Is+patients. Testing solely to MCI/MI would miss 47.3% (611/1292) of MI and 60.1% (466/776) of BIT allergic reactions. Retrospective cross-sectional study design and lack of follow-up data. Sensitization to isothiazolinones is high and concurrent sensitization to multiple isothiazolinone allergens is common.

Impact of dupilumab on patch test results and allergic contact dermatitis: A prospective multicenter study

Limited and conflicting data have been reported on the impact of dupilumab (DUPI) on patch test (PT) results and its efficacy against allergic contact dermatitis (ACD). This study was undertaken to analyze PT reactivities and relevance during treatment with DUPI to determine whether they could detect ACD in patients with uncontrolled or worsened atopic dermatitis (AD) who were receiving this agent. This prospective, multicenter study examined 76 DUPI-treated patients who had undergone PTs. The relevant information was collected during 3 visits. Overall, 36 patients (47%) had ≥1 positive PT reaction, and 142 PT results were positive. Twenty-three patients (30%) had ≥1 positive and clinically relevant PT result. Five of them had clinical eczema improvement after allergen avoidance. We compared the PT results of 36 patients before and during DUPI therapy, representing 1230 paired PT allergens, of which 1022 were the same, 34 were positive, 44 were lost, and 130 were uninterpretable. Because the number of patients included remains limited, our findings should be confirmed with a larger sample. Our results confirmed the usefulness of PTs for patients receiving DUPI, with good PT reproducibility. We suggest that all DUPI-treated patients with AD developing partial responses or experiencing symptom worsening should undergo PTs to look for contact sensitization.

Patterns of simultaneous contact allergies in patients with contact sensitization to oxidised linalool and oxidised limonene.

Contact allergy rates of linalool and limonene hydroperoxides (HPs) have increased. To demonstrate the patterns of simultaneous positive patch test (PT) reactions and prevalences of multiple contact allergies (MCAs) in patients with contact allergy to linalool and/or limonene HPs. A retrospective analysis of consecutive dermatitis patients in 2015-2020 was performed. Of all 4192 patients, 1851 had at least one positive PT reaction. Of these, 410 (22.2%) had MCAs, significantly related to a higher age (p-value = 0.003). Patients with an exclusively positive reaction to linalool HPs but not limonene HPs were shown to have MCAs (p-value <0.001, odds ratio (95% confidence interval) = 4.15 (3.01-5.73)). Patients with simultaneous contact allergies to both linalool and limonene HPs had contact allergies to many other screening and fragrance allergens. Simultaneous positive PT reactions to allergens in baseline series and fragrances are common in patients with the HPs contact allergy, especially linalool HPs. The pattern of simultaneous PT reactions principally suggested the co-sensitization of the cosmetic allergens.

Frequency and clinical relevance of contact allergy in dental patients.

While many studies have reported on occupational allergic contact dermatitis amongst dental personnel, studies on the relevance of patch testing in dental patients are scarce. To determine the frequency and clinical relevance of contact allergy in patients with intra- and perioral complaints. A total of 360 patients with intra- and perioral complaints suspected of having a contact allergy were patch-tested with the dental allergen series, European Baseline Series, and extended Amsterdam Baseline Series at Amsterdam University Medical Centers between January 2015 and November 2021. A total of 285 patients (79.2%) had a positive patch test reaction for either one (18.6%) or multiple allergens (60.6%). Sodium tetrachloropalladate was the most sensitising allergen with 98 patients (27.2%) testing positive, followed by nickel sulphate (23.3%), methylisothiazolinone (15.6%), and fragrance mix I (14.2%). Clinical relevance was found in 68 of 208 patients (32.7%), with patients having one (15.4%) or multiple (17.3%) patch test reactions clinically relevant to their (peri)oral complaints. Clinically relevant patch test reactions were frequently seen in dental patients. Although this study provides us with a better understanding on the frequency and clinical relevance of contact allergy in dental patients, further studies are needed to confirm our results.

Contact hypersensitivity to Indian standard patch test series correlates with disease severity among children with atopic dermatitis.

Background There is emerging evidence of a relationship between atopic dermatitis (AD) and allergic contact dermatitis (ACD), though the data available are scarce with conflicting viewpoints. We explored the occurrence of contact hypersensitivity among children with atopic dermatitis by patch testing them with the Indian standard series and tried to correlate the presence of contact hypersensitivity with the clinical severity of AD in these children. Methods In this single-centre, cross-sectional study, children between 6 months and 12 years diagnosed with atopic dermatitis were included and patch tested with the Indian standard series. Outcome parameters were the proportion of patients having positive patch-test reactions, the proportion of positive patch-test reactions for each allergen and factors associated with patch test positivity in atopic dermatitis. Results Of the 136 patients, 80 were boys. The mean age of the study population was 5.6 ± 3.2 years. Twenty-eight (20.6%) patients had patch test positivity at 96 h. Fragrance mix was the commonest allergen, followed by potassium dichromate, cobalt chloride hexahydrate and nickel. SCORing atopic dermatitis (SCORAD) was significantly higher in patients with positive patch tests as compared to patients with negative patch tests (P = 0.009). Conclusion Greater disease severity in atopic dermatitis was found to be associated with patch test positivity. Limitations Inability to establish relevance in about 50% of the patients was a limitation of our study. Follow-up data regarding the impact of allergen avoidance is not available.

CD09 Acrylate co-polymers: no cause for concern

Abstract Acrylate co-polymers are frequently used ingredients, believed to have low allergenic potential, present in a wide range of cosmetics, including skincare products, hairspray and nail varnish. Concerns have been expressed that individuals who are sensitized to (meth)acrylate monomers in ultraviolet (UV)-cured nail products may suffer elicitation reactions due to subsequent exposure to residual monomer impurities in acrylate co-polymers. The British Society for Cutaneous Allergy (BSCA) and the Cosmetic, Toiletry and Perfumery Association collaborated to investigate the allergenic potential of acrylate co-polymers. The BSCA prospectively audited data between 1 September 2021 and 1 September 2022 from the clinical databases of 20 patch test centres in the UK and Ireland, assessing the frequency of sensitization to three acrylate co-polymers. Patients with suspected or known allergy to (meth)acrylates and with facial dermatitis or (in some units) consecutive patients were tested to glyceryl acrylate/acrylic acid co-polymer 10% aqueous (aq.) (Lubrajel PF; United Guardian, Hauppauge, NY, USA), sodium polyacrylate 2% aq. (Cosmedia SP; BASF, Ludwigshafen, Germany) and EDT acrylates/C10-30 alkyl acrylate cross-polymer 2% aq. (Carbopol® ETD 2020 polymer; Lubrizol Advanced Materials, Wickliffe, OH, USA). During their manufacture, the pH of the patch test preparations was adjusted to within a range of 5.5–6.5. The antimicrobial preservative in the acrylate co-polymer patch test preparations, phenoxyethanol 1% aq. (Chemotechnique, Vellinge, Sweden), was also tested. Readings were carried out on days 2 and 4. The frequency of positive (1+/2+/3+), irritant and doubtful reactions was recorded. In total, 1302 patients were patch tested to the acrylate co-polymers. Of these, 335 were tested in addition to the (meth)acrylate series, 423 in addition to the facial and (meth)acrylate series and 277 in addition to the facial series and 267 were consecutively tested in addition to the baseline series. To glyceryl acrylate/acrylic acid co-polymer, there was one doubtful reaction in a patient allergic to multiple (meth)acrylates and one irritant reaction. To sodium polyacrylate, there were four irritant reactions, one doubtful reaction and one 1+ reaction; in all cases, relevance was unknown and there was no demonstrable (meth)acrylate allergy. There were no positive reactions to EDT acrylates/C10-30 alkyl acrylate cross-polymer. There was one irritant reaction to phenoxyethanol. In patients with positive patch test reactions to any (meth)acrylate (n = 67), there was no positive patch test to any acrylate co-polymer. Sensitization to these concentrations of acrylate co-polymers is rare. It is not possible to attribute dermatitis in (meth)acrylate-sensitized patients to a cosmetic ingredient with an International Nomenclature Cosmetic Ingredient name containing ‘acrylate co-polymer’.

Patch Testing to Chlorhexidine Digluconate, 1% Aqueous: North American Contact Dermatitis Group Experience, 2015-2020.

Background: Chlorhexidine is an antiseptic that may cause allergic contact dermatitis. Objectives: To describe the epidemiology of chlorhexidine allergy and characterize positive patch test reactions. Methods: This retrospective study analyzed patients patch tested to chlorhexidine digluconate 1% aqueous by the North American Contact Dermatitis Group, 2015-2020. Results: Of 14,731 patients tested to chlorhexidine digluconate, 107 (0.7%) had an allergic reaction; of these, 56 (52.3%) reactions were currently clinically relevant. Most (59%) reactions were mild (+), followed by strong (++, 18.7%) and very strong (+++, 6.5%). Common primary dermatitis anatomic sites in chlorhexidine-positive patients were hands (26.4%), face (24.5%), and scattered/generalized distribution (17.9%). Compared with negative patients, chlorhexidine-positive patients were significantly more likely to have dermatitis involving the trunk (11.3% vs 5.1%; P = 0.0036). The most commonly identified source category was skin/health care products (n = 41, 38.3%). Only 11 (10.3%) chlorhexidine reactions were occupationally related; of these, 81.8% were in health care workers. Conclusions: Chlorhexidine digluconate allergy is uncommon, but often clinically relevant. Involvement of the hands, face, and scattered generalized patterns was frequent. Occupationally related reactions were found predominantly in health care workers.

Patch Testing With Cobalt in Adults: A North American Contact Dermatitis Group Experience, 2001-2018.

Background: Cobalt is a recognized cause of allergic contact dermatitis (ACD); however, detailed information on patient characteristics, sites, and sources is lacking. Objective: The aim of the study is to assess trends in patch test reactions to cobalt and associated patient characteristics, common sources, and body sites affected. Methods: The study used a retrospective analysis of adult patients who were patch tested to cobalt by the North American Contact Dermatitis Group between 2001 and 2018 (n = 41,730). Results: Overall, 2986 (7.2%) and 1362 (3.3%) had allergic or currently relevant patch test reaction to cobalt, respectively. Patients with versus without an allergic patch test reaction to cobalt were more likely to be female, employed, have a history of eczema or asthma, be Black, Hispanic, or Asian, and have occupational-related dermatitis. The most commonly identified sources of cobalt in allergic patients included jewelry, belts, and cement, concrete, and mortar. Affected body site(s) varied by cobalt source among patients with currently relevant reactions. Occupational relevance was found in 16.9% of patients with positive reactions. Conclusions: Positive patch test reactions to cobalt were common. The most common body sites were the hands, and affected site varied by the source of cobalt.

A review of patch-test data over the period of eight years in the allergy and immunology department in Qatar.

Patch testing is the primary diagnostic approach for contact dermatitis,1 an inflammatory skin reaction caused by exposure to external irritants. The pathophysiology of contact dermatitis may entail an immunological response (hypersensitivity type IV), a non-immunological response (irritant contact dermatitis), or a mix of the two. The diagnosis of contact dermatitis requires a correlation between a positive patch test and clinical relevance.2 This study aims to determine the prevalence of allergy sensitization among adults in Qatar and the allergens most frequently associated with positive patch test findings. Retrospective analysis used patch testing data from 2015 to 2022. Of the 87 patients tested, 43 had at least one positive reaction (mean age 41.7; range 19-68). Females were 33 of the total patients (76.7%). Thirteen (30%) patients had two or more positive reactions. The most common allergen groups associated with positive patch test reactions were nickel sulfate no. 12 (27.9%), and all reactants were female. followed by gold sodium thiosulfate no. 10 (23.3%, F:M = 2.3), p-phenylenediamine no. 10 (23.3%, F:M = 1.5), and p-tert-butylphenol formaldehyde resin no. 7 (16.2%, F:M = 6). Twenty-six reactants had one or more allergic disorders (allergic rhinitis, asthma, drug allergy, insect bite allergy, or chronic idiopathic urticaria), and 11 had atopic dermatitis. Triggering agents for contact dermatitis vary among geographic regions and populations. This study gives an idea of the allergens that are the most common sensitizers among the contact dermatitis population in the adult allergy clinic in Qatar.

Patch Testing Results From the Massachusetts General Hospital Occupational and Contact Dermatitis Clinic, 2017-2022.

Background: Patch testing is gold standard for identifying the source of allergic contact dermatitis (ACD). Objective: To report patch testing results from the Massachusetts General Hospital (MGH) Occupational and Contact Dermatitis Clinic from 2017 to 2022. Methods: Retrospective analysis of patients referred to MGH for patch testing, 2017-2022. Results: In total, 1438 patients were included. At least 1 positive patch test (PPT) reaction was observed in 1168 (81.2%) patients and at least 1 relevant PPT reaction was observed in 1087 (75.6%) patients. The most common allergen with a PPT was nickel (21.5%), followed by hydroperoxides of linalool (20.4%) and balsam of Peru (11.5%). Sensitization rates statistically increased over time for propylene glycol and decreased for 12 other allergens (all P values <0.0004). Limitations: Retrospective design, single institution tertiary referral population, and variations in allergens and suppliers across the study period. Conclusion: The field of ACD is constantly evolving. Regular analysis of patch test data is crucial to identify emerging and diminishing contact allergen trends.

Allergic reactivity for different dilutions of eugenol in repeated open application test and patch testing.

Eugenol is a known contact sensitiser included in fragrance mix I. To assess the allergic reactivity to eugenol in different concentrations using patch test as well as repeated open application test (ROAT). Overall 67 subjects from 6 European dermatology clinics participated in the study. The ROAT was performed for 21 days twice a day, applying 3 dilutions of eugenol (2.7%-0.5%) and a control. Before and after the ROAT, patch testing with 17 dilutions of eugenol (2.0%-0.00006%) and controls was performed. Out of the 34 subjects with contact allergy to eugenol, 21 (61.8%) showed a positive patch test before ROAT was performed, the lowest positive concentration was 0.031%. The ROAT was positive in 19 (55.9%) of the 34 subjects, the time until a positive reaction occurred was negatively associated with the concentration of the ROAT solution, as well as with the allergic reactivity of the subjects as defined by patch testing. In the patch test after ROAT, 20 of the 34 test subjects (58.8%) showed a positive reaction. In 13 (38.2%) of the 34 test subjects, the patch test result was not reproduceable, still 4 (31.0%) of these 13 subjects developed a positive ROAT. Eugenol can provoke a positive patch test reaction in a very low dose; besides, this hypersensitivity may persist even if a former positive patch test is not reproduceable.

Patch testing hydroperoxides of limonene and linalool in consecutive patients-Results of the IVDK 2018-2020.

Hydroperoxides of limonene (Lim-OOHs) and linalool (Lin-OOHs) are potent contact sensitizers. To investigate the prevalence of positive patch test (PT) reactions to Lim-OOHs and Lin-OOHs in consecutive patients, their demographic factors and concomitant reactions. Between 7/2018 and 12/2020, Lim-OOHs 0.3% pet. and Lin-OOHs 1% pet. were patch tested in 5511 consecutive patients. We assessed PT reactivity and analysed data from patients with either positive or negative PTs to Lim-OOHs and Lin-OOHs. Positive PT results to Lim-OOHs (n = 170, 3.1%) and Lin-OOHs (n = 483, 8.8%) were frequent. Most of the positive reactions were weak (LimOOHs n = 134/LinOOHs n = 429), and even more frequently, doubtful (n = 252/n = 578) or irritant reactions (n = 81/n = 178) were documented. PT reactivity to Lim-OOHs and Lin-OOHs was increased in patients with irritant reactions to sodium lauryl sulphate (SLS). The proportion of leg dermatitis and concomitant positive reactions to fragrances and essential oils was increased in patients with reactivity to these hydroperoxides. The observed reaction pattern suggests that both test preparations display an irritant potential with an increased risk of false positive reactions. Preparations should be chemically monitored in order to reduce irritancy. Mindful interpretation of PT results and aimed patch testing of lower concentrations is recommended.

Contact sensitization to benzisothiazolinone: IVDK-data of the years 2002 to 2021.

Benzisothiazolinone (BIT; CAS no. 2634-33-5) is used as a biocide in various products, including water-based paints, metalworking fluids, and household products. In recent years, increasing sensitization rates have been observed in Europe. To describe a time trend of sensitization to BIT, analyse concomitant reactions, and identify patients with increased risk of BIT sensitization. Retrospective analysis of data from 26 739 patients patch tested with BIT, sodium salt, 0.1% petrolatum as part of several special test series within the Information Network of Departments of Dermatology (IVDK), 2002 to 2021. Positive reactions to BIT were noted in 771 patients (2.9%). Sensitization frequency varied over time and increased in recent years, peaking at 6.5% in 2020. Painters and metalworkers handling metalworking fluids, but not cleaners, had a significantly increased risk of BIT sensitization. From our data, there is no evidence of immunological cross-reactivity between BIT and other isothiazolinones. The increasing frequency of sensitization justifies adding BIT to the baseline series. More research on the clinical relevance of positive patch test reactions to BIT and the cause for the rising numbers of BIT sensitization is needed.

What should be considered during epicutaneous patch testing?

AbstractIndications for epicutaneous patch testing include the detection or exclusion of allergic contact dermatitis of the skin, transitional mucosa or oral mucosa, suspected delayed-type immune reactions to ingredients of implants, and certain drug reactions (maculopapular exanthema, symmetrical drug-related intertriginous and flexural exanthema [SDRIFE], acute generalized exanthematous pustulosis [AGEP], and fixed drug eruption). When available, allergen preparations that have been pharmaceutically tested and that are approved or marketable as medicinal products should be used. Existing diagnostic gaps can be closed by testing the patient’s own materials in a suitable preparation. Interferences of ultraviolet (UV) light exposure or drugs with patch test reactions have to be considered. In addition to the reading after 48 h and 72 h, a further reading between day 7 (168 h) and day 10 (240 h) is useful, since about 15% of the positive test reactions remain undetected without this late reading. All positive patch test reactions considered allergic must be evaluated with regard to their clinical relevance based on existing exposures.

Patch Testing of Thai Children with Eczema

Objective: To detect contact allergy rate and common allergens in Thai children presented with eczema. Materials and Methods: A total of 124 children, aged 1-15 years, were patch tested using a pediatric screening series of 16 allergens and relevant additional allergens. Data on clinical presentation, atopic history and test results were collected. Results: Contact allergy was found in 51 of 124 children (41.1%) presented with all forms of eczema. The common allergens were lanolin alcohol (8.9%), cocamidopropyl betaine (8.1%), nickel sulfate (7.3%), fragrance mix I (5.6%), formaldehyde (5.6%), thimerosal (5.6%), fragrance mix II (4.8%), cobalt chloride (4.0%), methylchloroisothiazolinone/methylisothiazolinone (2.4%), methylisothiazolinone (2.4%) and thiuram mix (2.4%). Nineteen of 50 atopic dermatitis patients (38%) showed positive patch test reactions. Conclusion: Allergic contact dermatitis is common in children. Both atopic and non-atopic patients can develop contact dermatitis. Patch testing should be performed in children presented with eczema regardless of contact dermatitis history.