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.

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.

Oral tolerance to contact allergens: a common occurrence? A review.

Experimental and clinical oral tolerance to contact allergens has been reported sporadically, most notably in respect of nickel, and is generally assumed to be an uncommon phenomenon. There has recently been increased understanding of the immunological mechanisms inducing and maintaining oral tolerance. There are several contact allergens, including fragrance, antioxidant, and preservative chemicals, to which subjects are exposed through both cutaneous and oral routes. We examine the possibility that oral tolerance to contact allergens may be more common than previously thought. Animal models of oral tolerance to contact allergens indicate that cutaneous exposure to small, subsensitizing doses of contact allergens might negate any subsequent attempts to induce tolerance by oral administration. Extrapolating these observations to common human practises raises the possibility that application of contact allergens (fragrances, preservatives and antioxidants) in consumer products used by children could prevent or inhibit the later acquisition of specific tolerance resulting from 'natural' dietary exposure after weaning. Existing data on formaldehyde may conflict with this theory, though this could be explained by allergen specificity. We propose that further work in this area is needed.

Adverse skin reactions to personal protective equipment against severe acute respiratory syndrome--a descriptive study in Singapore.

Severe acute respiratory syndrome (SARS) was first recognized in February 2003. It is the first severe and readily transmissible new disease to emerge in the 21st century. Healthcare workers in affected countries were exposed to the regular use of personal protective equipment (PPE) such as the N95 mask, gloves, and gowns. Our aim was to study the prevalence of adverse skin reactions to PPE among healthcare workers in Singapore during the SARS outbreak. Healthcare staff in the National Skin Centre and Tan Tock Seng Hospital were surveyed using questionnaires. Of those asked to participate, 322 (94.7%) agreed. 14.3% of the respondents were doctors, 73.0% nurses, and 12.7% other ancillary staff. Mean age of respondents was 32.4 years, with the majority being women (85.7%) and Chinese (53.7%). 109 (35.5%) of the 307 staff who used masks regularly reported acne (59.6%), facial itch (51.4%), and rash (35.8%) from N95 mask use. 64 (21.4%) of the 299 who used gloves regularly reported dry skin (73.4%), itch (56.3%), and rash (37.5%). The use of PPE is associated with high rates of adverse skin reactions. There is a need to find suitable alternatives for affected staff and to encourage awareness among staff of the role of dermatologists in their care.

Contact allergy to (meth)acrylates in the dental series in southern Sweden: simultaneous positive patch test reaction patterns and possible screening allergens.

Contact allergy to dental allergens is a well-studied subject, more so among dental professionals than dental patients. 1632 subjects had been patch tested to either the dental patient series or dental personnel series at the department of Occupational and Environmental Dermatology, Malmö, Sweden. Positive patch tests to (meth)acrylate allergens were seen in 2.3% (30/1322) of the dental patients and 5.8% (18/310) of the dental personnel. The most common allergen for both groups was 2-hydroxyethyl methacrylate (2-HEMA), followed by ethyleneglycol dimethacrylate (EGDMA), triethyleneglycol dimethacrylate, and methyl methacrylate. 47 (29 dental patients and 18 dental personnel) out of these 48 had positive patch tests to 2-HEMA. All 30 subjects who had a positive reaction to EGDMA had a simultaneous positive reaction to 2-HEMA. One dental patient reacted only to 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]propane (bis-GMA). From our data, screening for (meth)acrylate contact allergy with 2-HEMA alone would have picked up 96.7% (29/30) of our (meth)acrylate-allergic dental patients and 100% (18/18) of our (meth)acrylate-allergic dental personnel. The addition of bis-GMA in dental patients would increase the pick-up rate to 100%.

Can an imidazolidinyl urea-preserved corticosteroid cream be safely used in individuals hypersensitive to formaldehyde?

A topical corticosteroid preparation on the Swedish market, Flutivate cream, contains a fairly high concentration of formaldehyde (FA). In this study, we have investigated the clinical relevance of contact allergy to FA when treating an allergic eczema with Flutivate cream, containing an FA-releasing preservative. In a randomized, double-blind study, 7 patients hypersensitive to both FA and nickel repeatedly applied Flutivate cream containing FA or Betnovate cream not containing FA to areas of experimentally induced nickel dermatitis. 17 controls allergic to nickel, but not FA, went through the same procedure. In 29 per cent of the FA-allergic individuals, the experimental dermatitis healed when treated with Flutivate cream compared with 71 per cent of the controls (P = 0.04). The conclusion to draw from this study is that an individual hypersensitive to FA should not use the corticosteroid preparation Flutivate cream on dermatitis skin.

Metal allergy in Singapore.

This is a clinical epidemiologic study to determine the frequency of metal allergy among patch-tested patients in the years 2001-2003. The results are compared with those of previous studies. All patients diagnosed as having allergic contact dermatitis in the National Skin Centre, Singapore, from January 2001 to December 2003 were studied retrospectively. The frequency of positive patch tests to the following metals were nickel 19.9%, chromate 5.6%, cobalt 8.2% and gold 8.3%. The frequency of nickel allergy has been steadily rising over the last 20 years. The most common sources of nickel allergy are costume jewelry, belt buckles, wrist watches and spectacle frames. After declining from 1984 to 1990, chromate and cobalt allergies have also been steadily increasing subsequently. The most common sources of chromate allergy were cement, leather and metal objects. Most positive patch tests to cobalt are regarded as co-sensitization due to primary nickel or chromate allergies. There has been a steep increase in positive patch tests to gold from 2001 to 2003, which is difficult to explain because the relevance and sources of such positive patch tests can rarely be determined with certainty. There has been an overall rise in the frequency of metal allergy in the last 20 years.

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.

High frequency of simultaneous sensitivity to Disperse Orange 3 in patients with positive patch tests to para-phenylenediamine.

Cross-sensitization between para-phenylenediamine (PPD) and Disperse Orange 3 (DO3), among other textile dyes, has frequently been reported. We evaluated the frequency of simultaneous patch test reactions to PPD and a range of textile dyes. Retrospectively, we studied 128 patients who were patch test positive to PPD and who had also been tested to textile dyes. The dyes that most commonly also reacted were DO3 (46.1%) followed by Disperse Yellow 3 (21.9%). 80% of 55 patients who had a + + or stronger reaction to PPD also reacted to DO3. Dyes that were least likely also to react were Bismarck Brown (0%), Naphthol AS (1.06%), Disperse Yellow 9 (1.06%), Disperse Blue 3 (1.56%) and Disperse Red 11 (2.13%). We interpreted the simultaneous patch test reactions to PPD and DO3 as due either to cross-sensitivity proper, or to metabolic conversion of textile dyes in the skin to PPD.