Patch testing with nickel chloride in a hydrogel

Various concentrations of NiCl2 in a hydrogel were evaluated as a possible alternative to the standard patch test material of 5% NiSO4 pet. Patch test responses were recorded on a total of 430 patients with known or suspected contact allergy. A NiCl2 concentration of 1% or less in the hydrogel failed to elicit a response in some patients who reacted to 5% NiSO4 pet. The 2% NiCl2 hydrogel produced a small increase in response frequency and may reduce false-negative reactions. Along with the ability of the material to improve the topical bioavailability of nickel ions, more irritant reactions were observed. However, in cases with a positive history and a negative patch test with petrolatum, the hydrogel prepared from Methocel-E-4M seems to be a useful alternative vehicle for water-soluble allergens.     

Patch testing with metalworking fluids from the patient's workplace

In view of the wide variety of components currently used in metalworking fluids (MWF), relevant contact sensitizations may be overlooked, because commercially available MWF test series cannot cover the full spectrum. Hence, patch testing with MWF from the patient's workplace is an important additional diagnostic tool. However, recommendations on how to perform such patch tests vary. We retrospectively analyzed patch test data of the Department of Dermatology in Dortmund, 1992-2003. In 141 metalworkers tested because of suspected occupational contact dermatitis due to MWF, 829 patch tests with 306 samples of MWF were performed. Water-based MWF (wb MWF) were mainly tested in 2 dilution series, i.e. pure (workplace concentration), 10% aq. and 1% aq., and pure, 50% aq. and 10% aq. Positive reactions to wb MWF occurred in 27 patients. Patch testing with wb MWF at workplace concentration resulted in 16.1% (39/242) positive reactions, with a positivity ratio of 69% and a reaction index of 0. From the analysis of reaction patterns and concomitant reactions, we conclude that most of these positive reactions indicated true contact allergy. With lower concentrations, relevant allergic reactions may be missed. Neat oils were tested as is or diluted from 1 to 50% in olive oil, but no reactions at all were observed. For optimum benefit of patch testing with MWF from the patient's workplace, breakdown testing is recommended. To overcome the time-consuming difficulties associated with this procedure, we propose a centre for information and documentation of contact allergies due to occupational exposure. Furthermore, full declaration of MWF ingredients is desirable.     

Patch testing in discoid eczema

We report a retrospective study of patch testing in patients with discoid eczema. 48 patients with persistent or severe discoid eczema were patch tested. The mean age of patients was 45 years and the median duration of symptoms was 6 months. 24 patients (50%) had positive patch tests, and 16 of these (33%) were considered to be clinically relevant. The most common allergens implicated were rubber chemicals, formaldehyde, neomycin, chrome, nickel (5, 2, 2, 2, 2, 2 reactions, respectively). 13 of 16 patients were followed up by telephone in 1996, and 8/13 (61%) slated they had benefited from patch testing. This study suggests allergic contact dermatitis is relatively common in persistent discoid eczema, and allergen avoidance may be of benefit. We recommend patch testing should be considered for all patients with severe or persistent discoid eczema.     

Patch testing with natural rubber latex

The prevalence of Type I and Type IV hypersensitivity to rubber allergens in patients with stasis eczema and/or venous leg ulcers over an 18-month period was studied by prick and patch testing. Results from 109 patients were analysed. Positive patch tests were found in 71 patients (65%). Delayed-type hypersensitivity to rubber chemicals was found in 17 patients (15.6%). However, only 1 patient who had additional risk factors showed Type I hypersensitivity to natural rubber latex. We therefore conclude that, although Type IV hypersensitivity to rubber chemicals is relatively common in our patients, Type I hypersensitivity to natural rubber latex remains rare.     

Occupational dermatoses in workers exposed to resins based on phenol and formaldehyde

During December 1985 and February 1986, an investigation was carried out into skin diseases among workers in a plant producing decorative equipment built of paper sheets impregnated with resol resins based on phenol and formaldehyde (P-F-R). A questionnaire was sent to all 238 employees and it was answered by 218 (91.6%). Previous and current dermatoses were reported by 98 workers and 89 of these were examined and patch tested. The patch testing was conducted with a standard test series and products from the working environment and revealed contact allergy to P-F-R in 9 persons and to formaldehyde in 1. Besides these 10 individuals with occupational allergic contact dermatitis, occupational dermatoses were diagnosed in an additional 20 workers; irritant contact dermatitis in 19 and chemical burn in 1. In total, the figure for occupational dermatoses was 30 (12.6%).     

Patch testing with amalgam at various concentrations

27 patients with positive D3 reactions on patch testing to 3 mercury screening allergens were patch tested with 13 mercury patch test preparations, 6 inorganic and 7 organic, and amalgam 20% pet. The 13 patients (all women) showing positive reactions to 20% amalgam were then patch tested to reducing concentrations. 2 patients reacted down to 1%, 4 down to 2%, 4 down to 5%, 2 down to 10% and 1 only to 20%, a total of 10 of the 13 patients therefore reacting to the 5% concentration of amalgam. The appropriate patch test concentration of amalgam is discussed and the clinical significance and female preponderance of amalgam reactivity suggested as being worthy of further investigation.     

Patch testing with benzoyl peroxide: reaction profile and interpretation of positive patch test reactions

Background: Patch testing with benzoyl peroxide 1% pet. frequently leads to (weak) positive reactions, often with uncertain clinical relevance.
Objectives: To describe the pattern of patch tests reactions to benzoyl peroxide and to identify patients at risk of a positive reaction.
Methods: Retrospective analysis of data from the Information Network of Departments of Dermatology (IVDK), 1992–2007.
Results: Benzoyl peroxide 1% pet. was tested in 29 758 patients. Weak positive reactions (erythema, infiltration, possibly papules) occurred in 6.5%, and strong positive reactions (erythema, infiltration, vesicles) in 1.3%. According to logistic regression analysis, strong positive reactions to benzoyl peroxide were associated with leg or face dermatitis, work as dental technicians, young age and being female. Patients with atopic dermatitis had a significantly increased risk of weak positive reactions only.
Conclusions: Our analysis confirms that benzoyl peroxide 1% pet. is a problematic patch test preparation. Hence, clinical relevance of reactions to benzoyl peroxide has to be assessed very carefully. Patients with atopic dermatitis are particularly prone to irritant reactions to benzoyl peroxide. True allergic reactions may occur in dental technicians and following the treatment of leg ulcers with highly concentrated benzoyl peroxide in past. In contrast, widely used acne treatments with benzoyl peroxide seems to sensitize only rarely.     

Contact allergy to phenol-formaldehyde resins

Adverse reactions to phenol-formaldehyde resins include depigmentation, irritant dermatitis, chemical burns and allergic contact dermatitis. Allergic contact dermatitis from phenol-formaldehyde resin has mainly been ascribed to resins based on paratertiary-butyl phenol and formaldehyde, and such a resin is included in the ICDRG standard patch test series. When 1220 patients were patch tested with this resin as well as with 2 other phenol-formaldehyde resins, based on phenol and formaldehyde, 26 patients were positive to at least 1 resin. The figures for positive reactions to paratertiary-butyl phenol-formaldehyde resin and the 2 other resins were 0.8%, 1.0% and 3.0% (440 tested subjects), respectively. Therefore, a battery of phenol-formaldehyde resins should be used for screening purposes, since patch testing with the paratertiary-butyl phenol-formaldehyde resin is not sufficient to identify patients with contact allergy to phenol-formaldehyde resins. Several of the 26 patients were patch tested with the basic substances phenol, formaldehyde and paratertiary-butyl phenol, but only 1 positive reaction to formaldehyde was noted. The sensitizing capacity of 2-methylol phenol, 4-methylol phenol and 2,4,6-trimethylol phenol, all 3 compounds being possible ingredients of resins based on phenol and formaldehyde, was demonstrated; 5 of 14 resin positive patients reacted to at least 1 of these methylol phenols.     

Patch testing with colophony

Colophony (rosin) has been fractionated into 2 parts, an acidic and a neutral fraction. Routine patch testing with neutral components gives positive reactions at a 40% higher frequency than routine patch testing with colophony (20%) (w/w in pet.). A concentration of 60% colophony is suggested for routine patch testing.