Contact Dermatitis and Patch Testing Clinic
Atlal Al-Lafi (Chairman)
|Allergens for a patch testing set in Kuwait as
experienced at the contact dermatitis unit of As'ad Al-Hamad Dermatology Center
(formerly known as the Department of Dermatology), Al-Sabah Hospital:
Investigation of cases of suspected contact dermatitis shows the most prevalent sensitizers in the community. In Kuwait there have been no previous studies to establish a routine patch test tray for the most common allergens, For this reason we selected from the set of TROLAB allergens those reagents most likely to be incriminated in the etiology of contact dermatitis. Selection was based on the history, clinical presentation and investigation of the prevailing sensitizers in the community. The standard curatest patch strips of Lohmann were used.
For routine patch testing of cases of suspected allergic contact dermatitis, the European Standard set of 22 allergens is generally accepted. The spectrum of contactants, however, is varying in different countries and at different times in the same country.
In an attempt to find a patch test set that represents the most prevalent allergens in Kuwait, we analyzed the results of testing of 1000 consecutive patients of whom 632 had contact sensitivity to one or more allergens since 1977 until 1991 . No standard set was used, but reagents were selected on the basis of history, clinical presentation and investigation of the prevailing contactants in the community. The commonest sensitizers were metallic allergens (chromate, nickel, and cobalt) and perfume ingredients.
The protocol established by the ICDRG was followed. It was found that application of the patch for 48 hours caused � in many cases � erythema and miliaria at the site of plaster. Moreover, waiting for one hour fails to eliminate the effects of the patch. The best results were achieved by leaving the patch for 30 hours and reading the results after 48 or 72 hours. The reactions were scored according to the standard scoring system recommended by the International group.
Analysis of results of investigation of 1000 cases of suspected allergic contact dermatitis has shown that 632 cases gave positive patch test reactions to one or more test substances representing 63,2% of the series. Allergens that elicited reactions in more than 1% of positive cases were as follows:
Considering the sex ratio, 158 (71%) of chromate sensitive patients were males whereas with nickel females constituted 64.6% (104 cases).
Reactions to cobalt were always encountered concurrently with sensitivity to chromate in 27 cases, with nickel in 22 cases or with both in two cases. No case of sensitivity to cobalt alone was detected. Cobalt is a contaminant of nickel and cement and concomitant sensitivity may occur. Some authors, however, consider cobalt sensitivity as a phenomenon secondary to an already existing dermatitis or as a reflection of general skin vulnerability.
In the early period of our study, the fragrance mix was not available and we used three of its components namely cinnamyl alcohol, cinnamaldehyde and eugenol. Nevertheless many cases of perfume sensitivity failed to react to the test reagents but reacted to the brands used by the patients. The most offending native perfumes were those known as �Rose oil� and �stick oil�.
Of the rubber chemicals the most frequent allergen was mercapto mix and less frequent were carba and thiuram mixes. No reactions were elicited to naphthyl mix. This supports the view of Ketel regarding the low sensitization potential of this reagent.
In conclusion, the North American Contact Dermatitis Research Group suggested that a chemical be included in the screening tray if 1% or more of those tested exhibit positive reactions to it. In fact our cases were not tested to a constant tray but reagents were selected for each individual case on the basis of strong suspicion from the history and clinical presentation. We suggest a test set of 16 substances including chromates, nickel, cobalt, fragrance mix, balsam of Peru, paraphenylene diamine, mercapto mix, wool alcohols, formaldehyde, colophony, carba mix, ethylene diamine, trupentine, benzalkonium chloride, thiuram mix and chlorocresol.
We have listed 19 chemicals that elicited reactions among more than 1% of sensitized individuals. Considering that these include three components of the fragrance mix which can be substituted by that mix for screening and diagnostic purpose, therefore our test tray will include only 16 chemicals together with testing with pieces of the offending substances in cases of perfume, shoe leather or cloth dermatitis when necessary. Comparing our results with those published by the Danish group in 1989 who tested 2166 patients with the standard series of allergens, we notice that the most frequent eight allergens in Denmark are included in the most frequent eleven sensitizers in our series. In Denmark four of the allergens in the European standard test series failed to elicit reactions in 1% of those tested. In our series, nine of those allergens gave less than 1% of the positive results while three of the reagents outside the European standard set could elicit more than1%. This supports the view that the standard test can be modified according to the prevailing sensitizers in the community.
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