Photopatch testing in Singapore: A 10-year retrospective study.

BACKGROUND: Photopatch testing represents the gold standard for the diagnosis of photoallergic contact dermatitis (PACD). We aimed to identify common photoallergens in our tertiary dermatological referral centre from 2012 to 2021, to compare this to the preceding period studied, and data from other communities. METHODS: We conducted a retrospective review of all 90 patients who underwent photopatch testing at the National Skin Centre, Singapore, between 2012 and 2021. RESULTS: Of 90 patients, 19 (21.1%) were male, and the mean age was 41.6 years. Eighty-four (93.3%) underwent testing to our standard sunscreen series, 10 (11.1%) to our extended series, and 73 (81.1%) to their own items. Seventeen (18.9%) were diagnosed with PACD (i.e., photocontact allergy with present or past relevance), 12 (13.3%) with ACD, and 4 (4.4%) with photoaugmented ACD. Relevant reactions were commonest to oxybenzone (8, 9.5%) and mexenone (3, 3.6%). Eleven (15.1%) had PACD to their own items, with 3 of 4 (75%) tested to ketoprofen diagnosed with PACD and the remaining 1 (25%) with photoaugmented ACD. Age, race, sex, atopy, and site of involvement were not associated with photocontact allergy. Compared to the preceding time period, the overall frequency of photocontact allergy and PACD decreased, but rates of photoallergic reactions to individual photoallergens were not significantly different. CONCLUSION: Organic ultraviolet absorbers such as oxybenzone and mexenone remained the most relevant photoallergens. Personal item testing was valuable, and testing to ketoprofen should be considered.

Pediatric patch testing in a multi-ethnic Asian population: A retrospective review.

BACKGROUND: Pediatric allergic contact dermatitis (ACD) is increasingly prevalent. Patch testing is the gold-standard diagnostic investigation. The aims of our study were to describe the clinical profile of pediatric patients with ACD in a multi-ethnic Asian population and identify the common contact allergens. METHODS: This was a retrospective study involving children and adolescents aged 16 years or younger with clinically suspected ACD who underwent patch testing between January 2007 and March 2020 at two institutions in Singapore. Information pertaining to their demographics, atopy history, clinical presentation, and patch test results was analyzed. RESULTS: A total of 252 patients were included. The mean age was 10.9 years (1.0-16.7 years). The majority were Chinese (79.8%) and girls (57.5%). Many (66.3%) had atopic dermatitis (AD), which was mild. The most common presentation was an acral eczematous rash. The sensitization rate was 50.0%. The most frequent reactions were to nickel sulfate (49.2%) and fragrance mix (19.1%). The overall rate of relevant positive patch tests was 72.5%. Patients with AD were less likely to have a reaction to fragrance mix (p = .019) and more likely to have a reaction to disperse blue (p = .041). Compared to younger children, adolescents were less likely to have a positive patch test (p = .008). Indians were also less likely to have a positive reaction (p = .004). CONCLUSION: Metals and fragrances were the most common allergens causing childhood ACD in Singapore. Patients with AD were less likely to be sensitized to fragrances and more likely to be sensitized to disperse blue dye.

Comparison of Irritancy Potential of Sodium Lauryl Sulfate-free Aqueous Cream to Other Moisturizers: An Intraindividual Skin Occlusive Study.

Objective: We compared the irritancy potential of sodium lauryl sulfate (SLS)-free aqueous cream to SLS-containing aqueous cream and other moisturizers. Design: This was a double-blind, intraindividual occlusive study. SLS-containing aqueous cream; SLS-free aqueous cream; white soft paraffin; urea cream; Physiogel® (Stiefel Laboratories, Brentford, United Kingdom); QV cream (Ego Pharmaceuticals Pty. Ltd., Braeside, Australia); Cetaphil RestoraDerm® (Galderma Laboratories, Fort Worth, Texas); Ceradan® (Hyphens Pharma International Ltd., Singapore); normal saline; and SLS 1% aqueous were applied with Finn chamber occlusion to different sites on each participant's back for 72 hours. Skin assessments were carried out on Day 0 preapplication and Day 3 and Day 7 postapplication. Participants: Twelve healthy adult volunteers were included in this study. Measurements: Study subjects were clinically evaluated by an experienced dermatologist using a four-point severity scale to assess the severity of erythema, dryness, desquamation, stinging or burning, and pruritus. Corneometer® and transepidermal water loss (TEWL) readings were taken to assess skin hydration and skin barrier integrity, respectively. All measurements were performed on Days 0, 3, and 7. Results: Application of the SLS-free aqueous cream resulted in no significant changes in TEWL or Corneometer® readings throughout the study period. The SLS-containing aqueous cream resulted in a significant increase in TEWL from Day 0 to Days 3 and 7. All test moisturizer creams showed no significant changes in their clinical assessment scores. Conclusion: The results of our study indicate that SLS-free aqueous cream has a lower irritancy potential than SLS-containing aqueous cream, with the same level of maintenance of skin barrier integrity and hydration. SLS-free aqueous cream also appears to be less irritating to the skin than other non-SLS generic and commercial moisturizers tested.

Photopatch testing in Asians: a 5-year experience in Singapore.

BACKGROUND: Photopatch testing is important for diagnosing photoallergic contact dermatitis. We aimed to evaluate the use of photopatch test at the National Skin Centre, Singapore. METHODS: All patients who had photopatch tests done between 2007 and 2011 at the National Skin Centre were included. RESULTS: Twenty-two patients were included. The mean age was 40.2. Female : male ratio was 3.4. The ethnic groups were Chinese (68%), Malay (4%), Indian (14%) and others (14%). Ten out of 22 patients (45.5%) had a positive photopatch test. There were 20 positive photopatch test reactions found in these 10 patients, and all 20 positive reactions were of current relevance. The frequencies of the positive photopatch test reactions were 2-hydroxy-4-methoxybenzophenone (oxybenzone) (n = 6), 2-hydroxymethoxymethylbenzophenone (mexenone) (n = 3), 2-ethylhexyl-4-dimethylaminobenzoate (n = 1), ketoprofen gel (n = 1) and the patient's own product (n = 9). CONCLUSIONS: Our study suggests that sunscreen is the most common photoallergen to date as opposed to musk ambrette, which was the most common photoallergen in our earlier study in 1991-1993. This finding is similar to the recent European Multicentre Photopatch Test Study.

Correlation between stated and measured concentrations of acrylate and methacrylate allergens in patch-test preparations.

BACKGROUND: Contact allergy to acrylates and methacrylates is not uncommon. The allergy is confirmed by patch-testing patients with commercial patch-test preparations. OBJECTIVE: To investigate acrylate and methacrylate allergens used for patch testing in nine different dermatology departments from Europe, America, Asia, and Australia. METHODS: The acrylate and methacrylate (methyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, ethylene glycol dimethacrylate, and triethylene glycol diacrylate) allergen samples were analyzed with high-performance liquid chromatography to measure the allergen content. RESULTS: Variation in measured versus stated concentrations was seen in these samples. The ratio of measured to stated concentrations ranged from 0.11 to 1.1. Only 22 (63%) of 35 samples were within the arbitrary acceptable limits of 80 to 120% of the stated concentrations. CONCLUSION: The results may have implications for individual diagnosis and prevention and when test results from various centers are compared.

Plant dermatitis: asian perspective.

Occupational and recreational plant exposure on the skin is fairly common. Plant products and extracts are commonly used and found extensively in the environment. Adverse reactions to plants and their products are also fairly common. However, making the diagnosis of contact dermatitis from plants and plant extracts is not always simple and straightforward. Phytodermatitis refers to inflammation of the skin caused by a plant. The clinical patterns may be allergic phytodermatitis, photophytodermatitis, irritant contact dermatitis, pharmacological injury, and mechanical injury. In this article, we will focus mainly on allergy contact dermatitis from plants or allergic phytodermatitis occurring in Asia.

Screening for acrylate/methacrylate allergy in the baseline series: our experience in Sweden and Singapore.

BACKGROUND: No studies to specifically determine the prevalence of contact allergy to acrylates/methacrylates in patch tested populations have been published. OBJECTIVES: To determine the prevalence of acrylate/methacrylate allergy in all patients tested to the baseline patch test series. METHODS: Five acrylate/methacrylate allergens (2-hydroxyethyl methacrylate, methyl methacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, and 2-hydroxypropyl acrylate) were included in the baseline series for at least 2 years in Malmö and Singapore. RESULTS: Thirty-eight patients in total had reacted to acrylate/methacrylate allergens in the baseline series during the study period in both populations. In Malmö, there were 26 (1.4%) patients with positive patch tests to acrylate/methacrylate allergens, 14 of whom had relevant reactions. In Singapore, there were 12 (1.0%) patients with positive patch tests to acrylate/methacrylate allergens, but only 1 had relevant reactions. If we had not added acrylate/methacrylate allergens to the baseline series, we would not have patch tested 13/26 (50%) of the positive reactors in Malmö and 11/12 (92%) of the positive reactors in Singapore. The overall proportion of missed positive reactors would have been 24/38 (63%). CONCLUSIONS: The prevalence of acrylate/methacrylate allergy in our patch tested dermatitis populations is 1.4% in Malmö and 1.0% in Singapore.

Contact sensitization in patients with chronic venous leg ulcers in Singapore.

Contact sensitization rates are high in patients with chronic venous leg ulcers. Allergic contact dermatitis poses a significant hindrance to the healing of the wounds. There are no published studies examining the rate of contact sensitization in Asian patients. Our objective was to determine the rate of contact sensitization in patients with chronic venous leg ulcer in Singapore and the variation in the common allergens based on local practices in comparison with Western countries. 44 patients were patch tested to the National Skin Centre standard series, steroid series, medicaments, topical Chinese medicaments, and to modern wound dressings used. The overall rate of contact sensitization was 61.4%. The common allergen groups were topical antibiotics (18.2%) and topical traditional Chinese medicaments (TTCM) (15.9%). Individually, colophony (11.3%), Saw Hong Choon skin ointment (Kam Bo Med, Hong Kong, Hong Kong) (11.3%), Balsam of Peru (9.1%), and povidone iodine (9.1%) were among the most frequent allergens. The sensitization rate among users of TTCM was notably high (41%). A high rate of contact sensitization was found in our study, similar to previous reports from the West. TTCM play a major role as possible allergens in our patients. In Asian patients, a history of its usage should be elicited, and patch testing should include the commonly used TTCM where possible.

Patch testing of Singapore children and adolescents: our experience over 18 years.

This is a retrospective epidemiologic study of allergic contact dermatitis in children and adolescents in Singapore who had undergone patch testing from January 1, 1986 to December 31, 2003. A total of 2,340 patients below the age of 21 years had undergone patch testing. Of these, 1,063 (583 girls, 480 boys) were positive to one or more allergens. The most common allergens were: nickel (40%), thimerosal (15%), colophony (9%), lanolin (8%), cobalt (8%), fragrance mix (5%), and neomycin (4%). Each of these allergens will be discussed individually. This is the first study with over 1000 patients on this subject from Asia.

Barrier repair in chronic plaque-type psoriasis.

PURPOSE: To investigate barrier repair after mild trauma in lesional skin of psoriasis patients with chronic plaque-type disease and to compare this with non-involved psoriatic skin and normal controls. METHODS: Transepidermal water loss (TEWL) readings were taken from involved psoriatic skin and non-involved skin of psoriasis patients as well as the skin of normal controls. Three readings were performed at each site: the basal state, immediately after 20 tape strippings and 1 week post stripping. RESULTS: Higher baseline, post-stripping and 1-week recovery TEWL readings in psoriatic-involved skin compared to non-involved and normal control skin. No significant difference in barrier recovery rate in psoriatic-involved skin compared to non-involved and normal control. CONCLUSION: Although there appears to be a derangement of barrier function in lesional skin of psoriasis patients compared to non-lesional skin and the skin of healthy controls, the barrier recovery function of lesional psoriatic skin is still fully operational.

Correlation between laser Doppler perfusion imaging and visual scoring of patch test sites in subjects with experimentally induced allergic and irritant contact reactions.

PURPOSE: To compare laser Doppler perfusion imaging (LDPI) measurements in experimentally induced allergic contact reactions and irritant contact reactions. The degree of correlation between visual scores and LDPI measurements was also studied. METHODS: Fifteen patients with known contact allergy to nickel or fragrance were patch tested with nickel sulfate 5% pet., fragrance mix 8% pet., sodium lauryl sulfate (SLS) 0.5% pet., SLS 1.0% pet. and two empty control chambers. Visual readings and LDPI measurements were taken at 0, 48 and 96 h. RESULTS: There was a positive correlation between visual scores and LDPI measurement in the nickel sulfate and fragrance mix patch test sites. However, no correlation between visual scores and LDPI measurements was seen in the SLS 0.5% and SLS 1.0% patch test sites. There was no significant difference (P=0.125) in LDPI measurements between contact-allergic reactions and contact-irritant reactions. CONCLUSION: LDPI correlates with visual scoring in contact-allergic reactions, but not in irritant reactions. LDPI is not useful in distinguishing between allergic and irritant reactions.

Presence of formaldehyde in topical corticosteroid preparations available on the Swedish market.

The aim of this study was to investigate the formaldehyde content of topical corticosteroid preparations available on the Swedish market. 73 samples were analysed with the chromotropic acid (CA) method for semi-quantitative formaldehyde determination and 30 samples with a high-performance liquid chromatographic method. These included 24 ointments, 28 creams, 1 lotion, 6 liniments, 2 gels, 9 solutions, 2 mousses and 1 oral paste. Formaldehyde was found in 5 creams and 1 ointment. Sources of formaldehyde in these preparations were discussed. Isopropanol was identified as a probable source of yellow discoloration, leading to false-negative results with the CA method.

Relevance of positive patch test reactions in patients attending a dermatology tertiary referral centre.

Our purpose was to determine the proportion of relevant patch test reactions among all patch tested patients in the National Skin Centre (NSC), Singapore, from 1 January 1999 to 31 December 2000. A retrospective study was made of the patch test records of all patients patch tested in the study period. The proportion of relevant patch tests in this population was then determined. The allergens most likely to have present or past relevance were: nickel sulfate (79%), p-phenylenediamine (76%), colophonium (73%), cobalt chloride (68%) and potassium dichromate (67%). The most common allergens for each of the following relevance categories were as follows - present: p-phenylenediamine, thiuram mix, potassium dichromate; past: colophony, nickel sulfate, cobalt chloride; exposed: neomycin, gold sodium thiosulfate, fragrance mix and unknown: gold sodium thiosulfate, potassium dichromate, cobalt chloride. Evaluating relevance is difficult, and the results of relevance scoring vary widely between different groups. A consensus on the definition and standardization of the concept of relevance is needed.