Photoepicutaneous testing with the chamber method

The chamber test, so far successfully applied to epicutaneous testing, proved to be suitable for photoepicutaneous testing as well. A simple and reliable method was developed by dividing the test areas (after removing the tests from the skin) into two equal parts, one for ultraviolet irradiation and the other for dark control. Variations in the amounts of the test substances had a slight influence on the size but not on the strength of the reactions.     

Photoepicutaneous testing UV-induced protection against photoxic reactions in normal and vitiliginous skin: A clinical and histological study

The effect of erythemic UV irradiation on the phototoxic reactions caused by topical methoxsalen + UVA exposure was studied on normal skin, normal-looking skin of vitiligo patients, and vitiliginous skin. Although only slight histological changes were detectable 9 days after irradiation with 5 MED of erythemic UV, this pre-irradiation did induce protection against photoxic reactions in all skin types. This protection was clinically equal in all skin types; the slight differences were not statistically significant. Histological evaluation, however, showed a most conspicuous protective effect on vitiliginous skin. In all skin types the influence of UV pre-irradiation was confined to epidermal protection; the dermal phototoxic changes were unaffected.     

Contact allergy: Predictive testing in man

Predictive tests are of value in forecasting the response of a population to a sensitizer; diagnostic testing is used to determine what substances may actually be producing dermatologic problems. Skin sensitization predictive and diagnostic data for the eleven most frequently encountered skin sensitizers in Western Europe, Canada and the United States are reviewed. These compounds include two drugs (benzocaine and neomycin), two cosmetic ingredients ( p -phenylenediamine and balsam of Peru), four preservatives (formaldehyde, ethylenediamine, parabens and mercurials) and three ingredients of wearing apparel (nickel, chromium and thiram). Many of the data were collected by the North American Contact Dermatitis Group and the International Contact Dermatitis Research Group on tests with 1,200 and 4,825 dermatologic patients, respectively; the remainder were obtained by individual investigators with smaller groups of subjects. The data obtained by various investigators are discussed in relation 10 the factors which affect the extent and degree of sensitization which they can cause.     

Skin hyporeactivity in relation to patch testing

False-negative patch tests are clinically relevant. Skin hyporeactivity has been suggested as one possible cause. Evidence supports that failure to respond to a specific antigen might be due either to a faulty immune response, a defective inflammatory response or both. Thus, skin hyporeactivity may have clinical relevance in routine patch testing. Articles on this topic are infrequent and there is no index keyword for skin hyporeactivity as this phenomenon is poorly defined and investigated. This article summarizes several observations of skin hyporeactivity, reviews theories of possible mechanisms and discusses further consequences.     

Usefulness of skin testing in cutaneous drug eruptions in routine practice

Background: Cutaneous drug eruptions are common side-effects. The imputation score combining intrinsic (chronology, clinical and paraclinical signs) and extrinsic criteria used in Pharmacovigilance Centres is insufficient alone to identify with certainty a responsible drug.
Objective: To evaluate the imputation score before and after performing skin testing in patients with cutaneous drug eruptions.
Patients/Methods: A single-centre retrospective study was performed on 339 patients tested between 2001–2006. Imputation scores were calculated before and after skin tests for each cutaneous drug eruption according to the clinical type of skin eruption and the type of drug.
Results: Among 121 patients meeting inclusion criteria, 46% showed an increase of the imputation score as shown by 25/41 cases of maculo-papular exanthema, 4/11 cases of acute generalized exanthematous pustulosis and 17/41 cases of urticaria/anaphylaxis. The imputation score increased in 25/70 cases of the tested antibiotic drugs, in 14/56 cases of cardiovascular drugs, and it increased in 19 patients (34%) with I1 or I2 imputation scores before skin testing and in 29 (52%) with an I3 imputation score before skin testing.
Conclusions: Drug skin testing appeared useful in investigating cutaneous drug eruptions in routine practice, including not only drugs with a high imputation score (I3) but also those with a lower score (I1, I2). Drug skin testing should lead to oral rechallenge of drugs with negative tests in order to determine which drugs may be used safely.     

Softisan – a new vehicle for patch testing

Petrolatum is a good vehicle for many patch test allergens, because it is stable, unreactive, and allergy to it is rare (1, 2). Some difficulties exist, however, when water-soluble allergens are tested, because emulsifiers are often needed; these can change the properties of both the test material and the vehicle itself (3, 4). In the present study, we compared petrolatum with a new lanolin substitute based on vegetable fatty acids as a patch test vehicle for nickel sulphate.     

Clindamycin skin testing has limited diagnostic potential

We examined the role of clindamycin prick and intradermal skin testing in a tertiary care clinic population. Experience with diagnostic modalities such as prick and intradermal testing has been limited with clindamycin. A retrospective chart review was conducted for patients with immunologic reactions temporally associated with clindamycin who were referred to the Drug Safety Clinic (Toronto, Ontario). A total of 31 patients were identified who had undergone prick and intradermal skin testing. All 31 negative immediate prick and intradermal tests were followed by a 150 mg oral dose of clindamycin. 10/31 (32%) subjects had significant reactions to the oral clindamycin provocation. 2 patients reported delayed reactions at the clindamycin intradermal test sites. Our experience suggests that prick and intradermal skin testing is not adequate in identifying patients with previous allergic reactions associated with clindamycin. Oral provocation tests can be used in patients with histories of clindamycin adverse reactions; however, it should be offered on a risk-benefit basis.     

The role of vehicles in diagnostic patch testing

The correct selection of vehicles for patch testing is crucial in the evaluation of suspected allergic contact dermatitis. We reviewed the literature by using Grateful Med software for the years 1966–1992, utilizing the subjects "vehicles" and "allergic contact dermal his" or "patch tests". Vehicles can influence bioavailability of the chemicals and subsequently percutaneous absorption or interaction with allergens. There are methodological problems in interpreting studies, such as sample size, percutaneous absorption and clinical aspects. Our judgement, partially validated by the literature, suggested that improved delivery systems (such as via vehicles) might significantly increase optimization, reliability and reproducibility of patch tests.     

Prevalence and relevance of the positivity of skin prick testing in patients with chronic urticaria

Many patients with chronic urticaria (CU) worry that foods or other allergens are responsible for their urticaria. Skin prick testing (SPT) may be one of the investigations used to provide a clear illustration. The purpose of our study was to assess the prevalence of positivity of SPT to food allergens and aeroallergens and their relevance in patients with CU, in order to demonstrate the diagnostic value of SPT in CU. We retrospectively reviewed case record forms of patients with chronic ordinary urticaria who underwent SPT in the Urticaria Clinic, Siriraj Hospital, during the period 2000-2004. The studied allergens included 16 food allergens and 12 aeroallergens. Eighty-eight patients were enrolled. The prevalence of positive SPT among patients with CU was 47.7%. Patients who had personal histories of atopy had statistically significant positive SPT results compared with patients who had negative SPT. Of 88 patients, 26 patients (30%) gave positive results to food allergens, 36 patients (41%) gave positive results to aeroallergens and 20 patients (22.7%) gave positive results to both food and aeroallergens. One-third of the subjects (34.6%) who had positive SPT results to food allergens had clinical relevance of food allergy in some systems but only one patient had clinical relevance of food-induced urticaria. Half of the patients who had a history of aeroallergen sensitivity gave a positive SPT response for aeroallergens; however, there was no clinical relevance to their CU. Our study showed that the prevalence of positive SPT to food allergens and aeroallergens in patients with CU was common but had little clinical relevance to CU.     

Food allergy testing in infantile eczema: A clinical approach and algorithm

The complex relationship between food allergy and infantile eczema has prompted divergent approaches to investigating potential food triggers in eczematous patients. It is well recognised that a significant proportion of infants with eczema have immunoglobulin E‐mediated food allergy, reported to range between 20–80%. Determining whether certain foods trigger an eczematous flare in individual infants with eczema is difficult. For all infants with eczema, good skin care is the mainstay of treatment but identifying and avoiding triggers (both allergic and non‐allergic) is important in some infants. Given this, we have a developed an algorithm that can be used by dermatologists in the investigation and management of food allergies in infantile eczema. Issues such as patient selection, investigation and elimination diets are addressed, with reference to relevant evidence in the literature. Our aim is to provide dermatologists with a framework to manage food allergies in infantile eczema, allowing the problem to be addressed with confidence.     

Routine patch testing with cadmium chloride

During a 22-month period, 2.0% cadmium chloride in distilled water was included in our routine patch test series. Twenty-five of 1502 eczema patients showed reactions (1.7 %), but none had any relevant history. At serial dilution test only one patient reacted to 1.0 % cadmium; all the other dilutions applied gave negative reactions. Analysis by atomic absorption spectrophotometry of the cadmium chloride used for patch testing showed that it contained less than 1 μg/g of chromium, copper, cobalt and nickel. The conclusion is that no certain case of contact allergy to cadmium chloride has been revealed. An experimental study using the guinea pig maximization test is in progress.     

Further studies of effects of vehicles and elicitation concentration in experimental contact sensitization testing in humans

Further confirmation of the effects of vehicles and elicitation concentration in experimental contact sensitization testing with fragrance ingredients is reported. A dose-response relation was seen when sensitized human subjects were challenged with dihydrocoumarin, alantroot oil and diethylmalleate. Furthermore, alcohol was shown to be a more effective vehicle than petrolatum, when cinnamon bark oil, vetiver acetate and diethylmalleate were used in predictive tests. The relation of these findings to risk-benefit judgments is discussed briefly.     

Erythema multiforme reaction to patch testing

A young woman developed erythema multiforme in association with multiple patch test reactions. Sequential patch testing revealed 2 true positive reactions (colophony and fragrance mix), and was not associated with flare of erythema-multiforme-type lesions. The development of erythema multiforme should be included in the list of possible adverse reactions to patch testing, albeit a rare occurrence.     

Dosage considerations in patch testing with liquid allergens

This study examines reproducibility of water and ethanol drop volumes from plastic squeeze dropper bottles, examines the difference in drop volumes between commonly used liquid patch test solutions, and evaluates the volumes of water and ethanol needed to saturate Finn and IQ Chamber filter papers. 2 plastic squeeze dropper bottles recommended for use in patch testing have poor reproducibility compared to other bottles tested. 3 aqueous allergens tested (formaldehyde 1%, methylchloroisothiazolinone/methylisothiazolinone 0.01%, and dimethylol dihydroxyethyleneurea 4.5%) have drop volumes equivalent to water. Smaller drop volumes are produced by ethanol, hydrocortisone butyrate 1% in ethanol, cocamidopropyl betaine 1% a.q., and propylene glycol 30% a.q. Filter paper saturation volumes using distilled water are 16-19 micro L in standard Finn Chambers and 29-35 micro L in IQ Chambers. Ethanol saturation volumes are slightly lower. Previously recommended volumes of application for aqueous allergens of 15 micro L for standard Finn Chambers and 25 micro L for IQ Chambers (slightly below the filter paper saturation points) are appropriate. Selection of dropper bottles should consider drop volume reproducibility, differing drop volumes for different allergens, and the patch test chamber system being used.