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.

Pattern of contact sensitization in patients with and without atopic dermatitis in an Asian dermatology center.

BACKGROUND: Although the traditional understanding is that contact sensitization is less frequent in patients with atopic dermatitis (AD), recent studies have shown similar or higher rates of positive patch-test results in AD patients. OBJECTIVES: We sought to characterise the pattern of contact sensitization in patients with and without AD and evaluate the association between AD and contact sensitization. METHOD: This was a single-center, 10-year retrospective review of patients who underwent patch testing between 2007 and 2017. RESULTS: There were 4903 patients (male-to-female ratio = 1:1.4; mean age 40.1 years) included. About half (2499, 51.0%) of all patients developed at least one positive reaction. The top five frequent reactions were to nickel sulfate (45.4%), potassium dichromate (16.0%), p-phenylenediamine (13.4%), Myroxylon pereirae (11.8%), and fragrance mix I (11.2%). The overall prevalence of contact sensitization was not significantly different between patients with or without AD. Patients with AD were less likely to develop contact allergies to budesonide and thiuram mix, and more likely to develop contact allergies to potassium dichromate. CONCLUSIONS: Contact sensitization was detected in 50% of patients who were patch tested. Nickel sulfate was the most frequently sensitizing allergen. The prevalence of contact allergies in atopic patients is comparable to that in non-atopic patients.

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.

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.

High frequency of false-positive reactions in attempted patch testing with acrylate/methacrylate mixes.

BACKGROUND: Although acrylate/methacrylate allergy has been frequently reported, until now patch testing with this group of allergens has been unwieldy, requiring the application of large supplementary series in most centres. OBJECTIVES: To formulate and evaluate two mixes of acrylate/methacrylate allergens in three centres (Malmö, Singapore, and Leuven). PATIENTS/MATERIALS/METHODS: All patients tested with the baseline series during the study period were also patch tested with the mixes. Mix 1 consisted of: triethyleneglycol diacrylate (TREGDA) 0.1% wt/wt, 2-hydroxyethyl methacrylate (2-HEMA) 1.0% wt/wt and ethyleneglycol dimethacrylate 1.0% wt/wt in petrolatum. Mix 2 consisted of: TREGDA 0.1% wt/wt and 2-HEMA 2.0% wt/wt in pet. The separate components of the two mixes were also tested simultaneously. RESULTS: There were 25 (5 males; 20 females) positive reactions to mix 1 with 16 in Malmö, 8 in Singapore, and 1 in Leuven. Positive reactions to mix 2 were seen only in Malmö, in 8 female patients. Thus, the positive reaction rate for mix 1 was 8.3% overall (Malmö 7.7%, Singapore 18.6%, and Leuven 2.1%), and that for mix 2 was 2.7% overall (Malmö 3.8%, Singapore 0%, and Leuven 0%). Of the 16 positive reactions to mix 1 in Malmö, only 4 were considered to be true allergic reactions, as the component allergen testing gave totally negative results in 12/16. For mix 2, only 3/8 positive reactions were considered to be true allergic reactions, as the component testing was negative in 5/8. Many doubtful (10-20%) and positive but non-allergic reactions were recorded, leading to early termination of the study. CONCLUSIONS: Although this was an unsuccessful attempt to formulate an acrylate/methacrylate mix, our experience will be useful for those embarking on future attempts to do this.

Occupational dermatoses in restaurant, catering and fast-food outlets in Singapore.

BACKGROUND: The restaurant industry is a rapidly growing sector in Singapore and workers in this industry are trained in culinary skills but not on recognition of safety and health hazards and their control measures. Anecdotal clinical evidence has suggested an increased prevalence of occupational dermatoses among restaurant workers. AIMS: To determine the prevalence and risk factors for contact dermatitis and burns among restaurant, catering and fast-food outlet (FFO) staff. METHODS: Workers were interviewed and then clinical examination and patch and/or prick tests were conducted in selected individuals. RESULTS: In total, 335 of 457 workers (73% response) were interviewed and 65 (19%) had occupational dermatitis or burns and were examined. Of these, contact dermatitis was the commonest diagnosis, with a 12-month period prevalence of 10% (35 workers) and 3-month period prevalence of 8% (26 workers). All 35 workers had irritant contact dermatitis (ICD) and there were no cases of allergic contact dermatitis. The adjusted prevalence rate ratios of risk factors for ICD were 2.78 (95% CI 1.36-5.72) for frequent hand washing >20 times per day, 3.87 (95% CI 1.89-7.93) for atopy and 2.57 (95% CI 1.21-5.47) for contact with squid. The 3-month period prevalence for burns was 6% (20 workers). Ten workers had other occupational dermatoses such as work-related calluses, paronychia, heat rash and allergic contact urticaria to prawn and lobster. CONCLUSIONS: ICD and burns are common occupational skin disorders among restaurant, catering and FFO workers.

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.

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.

The role of topical traditional chinese medicaments as contact sensitisers in chronic venous leg ulcer patients.

INTRODUCTION: Leg ulcers are a chronic condition affecting the older population. In Singapore, the use of topical traditional Chinese medicaments (TTCM) is common amongst those older than 65 years of age. We study the role of TTCM as contact sensitisers in patients with chronic venous leg ulcers and its impact in the clinical management of these patients. MATERIALS AND METHODS: Patients with chronic leg ulcers attending the Wound and Ulcer Clinic at the National Skin Centre (NSC) between October 2005 and April 2006 were patch-tested to the NSC TTCM series. They were also patch-tested for other allergens from the NSC Standard Series, Medicament Series, Steroid Series and wound dressings. RESULTS: A total of 44 patients were patch-tested. Seventeen of the 44 (38.7%) patients were using or had used at least 1 TTCM. Seven patients (15.9%) had at least 1 positive patch test (PT) reading to TTCM, giving a sensitisation rate of 41% (7 of 17). A significantly high proportion of the patients, 94.1% (16 of 17) with a positive history of TTCM usage had at least 1 positive PT reading compared to those without a history of TTCM usage, 45.8% (11 of 24). CONCLUSION: TTCM play an important role as contact sensitisers in our patients with chronic venous leg ulcers and may be a significant factor in non- or poor-healing leg ulcers. In such patients, a history of TTCM usage should be sought for and patch testing should include the commonly used TTCM where relevant.

Circadian and ultradian (12 h) variations of skin blood flow and barrier function in non-irritated and irritated skin-effect of topical corticosteroids.

The skin is the organ that receives the greatest exposure to light and shows a high-amplitude circadian rhythm in epidermal cell proliferation. We have previously demonstrated that the skin barrier function has a significant circadian rhythm. Corticosteroids (CS) are the most commonly used topical treatment in dermatology. Time-dependent differences in their efficacy and side-effects would be of considerable interest. The aims of the current study were to examine time-dependent cycles in the effect of topical CS application in healthy and irritated skin on skin blood flow and its relationship to barrier function. Twenty clinically healthy, diurnally active subjects were examined at eight and nine time points over a 24 or 28 h span respectively, using non-invasive skin bioengineering techniques of laser Doppler imaging, a transepidermal water loss (TEWL) device and a skin thermometer in a 28 h session. The results of this current study demonstrate circadian and ultradian (12 h) variations in skin blood flow. A significant correlation was found between skin temperature and skin blood flow but not with TEWL. Circadian and ultradian rhythms are maintained during treatment with high-potency and mid-potency CS in healthy skin. These rhythms persist during stratum corneum disruption with and without CS application.

Allergic contact dermatitis from chlorhexidine.

Although chlorhexidine is a widely used substance, allergic contact dermatitis from chlorhexidine has rarely been reported. Our objective was to study all cases of allergic contact dermatitis from chlorhexidine that were seen at St John's Institute of Dermatology from January 1983 to June 2002. The case records of all patients with positive patch-test reactions to chlorhexidine during the study period were retrieved. The clinical presentation, strength, and relevance of the positive patch-test results as well as possible sources of exposure were studied. There were five cases of allergic contact dermatitis from chlorhexidine during the study period; three of these patients had positive patch-test reactions to chlorhexidine that were of current relevance. The possible sources of exposure included Hibisol, Hibiscrub, a chlorhexidine spray, and peri- and postoperative antiseptic solutions. We concluded that allergic contact dermatitis from chlorhexidine is rare. However, when it occurs, it may cause a severe dermatitis reaction.

Contact sensitivity to preservatives in Singapore: frequency of sensitization to 11 common preservatives 2006-2011.

BACKGROUND: Preservatives are indispensable agents used to prevent bacterial and fungal contamination of cosmetics, personal care products, domestic preparations, and industrial products. OBJECTIVE: We evaluated patch-test data at the National Skin Centre, Singapore, from 2006 to 2011 to identify the trends in preservative contact allergies. METHODS: All patients with suspected contact dermatitis were patch tested to 4 preservatives within the modified European standard series. Patients were also tested with 7 preservatives from our special series if clinically indicated. RESULTS: Three thousand one hundred seventy-seven patients were tested to preservatives in the standard series. Sensitization frequencies were all greater than 1%: parabens (2.58%), methylchloroisothiazolinone/methylisothiazolinone (1.75%), quaternium 15 (1.43%), and methyldibromoglutaronitrile (1.2%). There was no change in trends in sensitization frequencies from 2006 to 2011, with no increase in sensitization frequency to methylchloroisothiazolinone/methylisothiazolinone. The sensitization frequencies for methyldibromoglutaronitrile/phenoxyethanol and diazolidinylurea were 2.03% and 1.37%, respectively, and remained less than 1% for bronopol, imidazolidinyl urea, and 2-phenoxyethanol. A rate of 0% was seen for 1,3-dimethylol-5,5-dimethyl hydantoin and formaldehyde; 9.4% of positive patch-test results became positive only at day 7. CONCLUSIONS: Preservatives are common causes of allergic contact dermatitis. This should be considered when introducing new preservatives into the market. Day 7 readings are important to detect late reactions.

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.