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Background: Patch testing for multiple cross-reactive allergens for allergic contact dermatitis (ACD) may not be necessary because of copositivity., Objectives: We evaluated the formaldehyde group allergens to determine the optimal, most cost-effective allergens to test., Methods: A retrospective analysis of Mayo Clinic (1997-2022) examined the well-established copositive formaldehyde group: formaldehyde, quaternium 15, hexahydro-1,3,5-tris(2-hydroxyethyl)triazine, diazolidinyl urea, imidazolidinyl urea, toluenesulphonamide formaldehyde resin, DMDM hydantoin, and ethyleneurea melamine formaldehyde mix. Patch Optimization Platform identified which single formaldehyde-related allergen optimally captures patients with clinically relevant ACD. Next, Patch Optimization Platform determined the optimal additional 1, 2, 3, etc. allergens. Cost per patch test was $5.19 (Medicare 2022)., Results: A total of 9832 patients were tested for all listed allergens, with 830 having positive patch test results. Patch Optimization Platform determined that quaternium 15 alone captures 53% of patients with ACD to the formaldehyde group; adding the optimal second allergen (formaldehyde 1%) captures 78%; the optimal 5 top allergens capture >94% of patients. The incremental cost per additional diagnosis increased up to 44-fold as the number of allergens tested increased., Limitations: Data are from a single institution, and the cost per test was fixed according to Medicare Part B in 2022., Conclusions: For diagnosing ACD, we recommend considering an optimized allergen selection algorithm., Competing Interests: Conflicts of interest None disclosed., (Copyright © 2024 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved.)

Background: Allergic contact Dermatitis (ACD) is a common condition within the pediatric population. Patch testing is an important way to identify relevant allergens. Objective: To provide an update of the common contact allergens seen in children based on patch testing data at our institution from 2016 to 2020. Methods: We performed a retrospective analysis of patch test data from children aged 1-18 years from 2016 to 2020 at Mayo Clinic. Reaction rates were compared to the rates reported by the Pediatric Contact Dermatitis Registry (PCDR). Results: One hundred ninety-two children aged 1-18 were patch tested to various allergens. A total of 15,457 allergens were tested, with 291 positive tests. The top 5 allergens with highest positive reaction rates were hydroperoxides of linalool, hydroperoxides of limonene, methylisothiazolinone, nickel, and cobalt. Seven of the top 38 allergens with the highest reaction rates are not currently included in the Mayo Clinic Pediatric Patch Test Series, and 11 are not currently included in the Pediatric Baseline Series (as developed by the Pediatric Contact Dermatitis Workgroup). Conclusions: Patch testing is a useful tool to diagnose children with ACD. With new products and exposures, there is an opportunity to expand current pediatric patch testing series.

Background: A major question in patch testing is when to perform the final reading. Our current standard practice is to place patches on day 1, remove them on day 3, and perform readings on days 3 and 5. For certain allergens, another reading is performed sometime from days 7 to 14≥., Objectives: The aim of the study was to identify allergens with positive reactions on day 5 that were negative on day 7 or later and allergens with negative reactions on day 5 that were subsequently positive on day 7 or later., Methods: We reviewed records of patients who underwent patch testing from January 2007 to December 2016 at Mayo Clinic with readings on day 5 and day 7 or later., Conclusions: In total, 131 allergens had positive reactions on day 5 that were negative on day 7 or later, and 58 allergens had negative reactions on day 5 that were positive on day 7 or later. Twenty-five allergens had significantly higher reaction rates on day 5 than day 7 or later. Our standard practice is to perform readings on days 3 and 5 and on days 3, 5, and 7 or later for series containing metals. Readings on days 3, 5, and 7 or later should also be considered for acrylates.

Background: Patch testing to a standard (baseline) series of allergens is the screening tool used to identify culprit allergens in patients with contact dermatitis. The allergens and concentrations used in a standard series are constantly evolving to be most relevant to the patients being patch tested., Objective: The aim of this study was to analyze the 2011-2015 patch test results of the Mayo Clinic standard series., Methods: We retrospectively reviewed patch test reactions of standard series allergens from 2011 through 2015 and compared these results with the 2011-2012 and 2013-2014 North American Contact Dermatitis Group (NACDG) reports., Conclusions: Of 2582 patients included, 1566 (60.7%) had at least 1 positive reaction, and 516 (20.0%) had at least 1 irritant reaction. The 15 allergens with the highest reaction rates (from highest to lowest) were nickel sulfate hexahydrate, methylisothiazolinone, Myroxylon pereirae resin, neomycin sulfate, cobalt (II) chloride hexahydrate, benzalkonium chloride, fragrance mix I, potassium dichromate, bacitracin, methylchloroisothiazolinone/methylisothiazolinone, carba mix, formaldehyde, p-phenylenediamine, quaternium-15, and methyldibromo glutaronitrile. Twelve (80%) of these allergens were also in the top 15 of the most recent NACDG report; the 3 allergens not in the NACDG top 15 allergens were potassium dichromate, benzalkonium chloride, and methyldibromo glutaronitrile (the latter 2 allergens are not included in their series).

Background: Propylene glycol (PG) is a solvent, vehicle, and humectant being used increasingly in a wide array of personal care products, cosmetics, and topical medicaments. Propylene glycol is a recognized source of both allergic and irritant contact dermatitis., Objective: The aim of the study was to report incidence of positive patch tests to PG at Mayo Clinic., Methods: We retrospectively reviewed records of all patients patch tested to PG from January 1997 to December 2016., Results: A total of 11,738 patients underwent patch testing to 5%, 10%, or 20% PG. Of these, 100 (0.85%) tested positive and 41 (0.35%) had irritant reactions. Patients also tested to a mean of 5.6 concomitant positive allergens. The positive reaction rates were 0%, 0.26%, and 1.86% for 5%, 10%, and 20% PG, respectively, increasing with each concentration increase. The irritant reaction rates were 0.95%, 0.24%, and 0.5% for 5%, 10%, and 20% PG, respectively., Conclusions: Propylene glycol is common in skin care products and is associated with both allergic and irritant patch test reactions. Increased concentrations were associated with increased reactions.

Background: Patch testing is essential for identification of culprits causing allergic contact dermatitis., Objective: We sought to identify trends and allergen changes in our standard series during 2006 to 2010, compared with our previous report (2001-2005)., Methods: We conducted a retrospective review of patch-test results., Results: A total of 3115 patients were tested with a mean of 73.0 allergens. Since our prior report, 8 allergens were added to the standard series; 14 were deleted. Significantly higher rates of allergic positive reaction were documented for carba mix, 3%, and Disperse Orange 3, 1%. Rates were lower for 10 allergens: neomycin sulfate, 20%; gold sodium thiosulfate, 0.5%; hexahydro-1,3,5-tris(2-hydroxyethyl)triazine, 1%; disperse blue 124, 1%; disperse blue 106, 1%; diazolidinyl urea, 1%; hexylresorcinol, 0.25%; diazolidinyl urea, 1% aqueous; 2-bromo-2-nitropropane-1,3-diol, 0.25%; and lidocaine, 5%. Many final patch-test readings for many allergens were categorized as mild reactions (erythema only). Overall allergenicity and irritancy rates declined significantly since our prior report. Results were generally comparable with those in a North American Contact Dermatitis Group report from 2005 to 2006., Limitations: This was a retrospective study; there is a lack of long-term follow-up., Conclusions: Since our previous report, our standard series composition has changed, and overall rates of allergenicity and irritancy have decreased. Notably, many final patch-test readings showed mild reactions., (Copyright © 2013 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.)