H. R. Smith

Irritant dermatitis, irritancy and its role in allergic contact dermatitis

Summary Irritant contact dermatitis is the clinical result of sufficient inflammation arising from release of pro‐inflammatory cytokines from skin cells (principally keratinocytes) in response to (usually) chemical stimuli. Different clinical forms may arise. The three main pathophysiological changes seen are skin barrier disruption, epidermal cellular changes and cytokine release. An important role of irritancy in allergic contact dermatitis (ACD) comes from earlier animal and human studies. Evidence is outlined which is consistent with a ‘danger model’ of ACD rather than one based on a traditional ‘self–nonself’ immune model. In such a model an antigenic signal will produce sensitization only in the presence of a danger signal; in the absence of a danger signal tolerance will occur. We propose that the danger signal in ACD is cytokine release from nonimmune skin cells (principally keratinocytes) and that both the antigenic and ‘danger’ signals arises from the hapten.

A retrospective analysis of contact allergy to lanolin

Backgroundu2003Lanolin is often stated to be an important sensitizer but some of the available literature is based on the analysis of high‐risk patients.Objectivesu2003To analyse the frequency of contact allergy to lanolin (wool alcohols) in a central London teaching hospital patch‐test population.Methodsu2003Review of 24,449 patients recorded on our database during 1982–96 who were tested with a standard series containing 30% wool alcohols.Resultsu2003The mean annual rate of sensitivity to this allergen was 1·7%. The wool alcohols‐allergic group contained a higher proportion of females (Pu2003<u20030·05), and the mean age of both males and females (48·4 and 49·2 years) was higher than that of non‐wool alcohols‐allergic patients (41·4 and 35·9 years; Pu2003<u20030·0005). There was no difference in atopic eczema status between these groups. The highest prevalence of allergy to wool alcohols was among patients with lower leg dermatitis (6·0%; 95% confidence interval, CI 4·46–7·54), followed by those with anogenital dermatitis (3·23%; 95% CI 1·81–4·65). There was an unexplained decline in the rate of positive patch tests to Amerchol® L‐101. However, some patients who reacted to this were negative with wool alcohols, so it may be a useful additional test reagent. The mean rates of allergy to Eucerin® (0·65% per annum) and 50% hydrogenated lanolin in petrolatum (1% per annum) were low, and we no longer use these as test reagents.Conclusionsu2003This study illustrates that lanolin sensitization has remained at a relatively low and constant rate even in a high‐risk population (i.e. patients with recent or active eczema).

Irritant thresholds in subjects with colophony allergy

The factors which determine individual susceptibility to the development of allergic contact dermatitis (ACD) are not well defined. Since it is known that the presence of skin irritation is well‐documented as a promoter of sensitization, the sensitivity to irritation of subjects with ACD has been compared with a normal control group. Whilst 78% of those with a positive patch test reaction to the contact allergen colophony (colophonium) responded to a concentration of no higher than 2.5% sodium lauryl sulfate (SLS), only 44% of the matched control group reacted at this level of SLS. Thus, the results are consistent with the hypothesis that individuals with enhanced susceptibility to skin irritation are also more liable to develop allergic skin reactivity.

Contact allergy to methyldibromo glutaronitrile presenting as severe scalp seborrhoeic eczema.

EuxylAK400 is a biocide containing 2 active ingredients, phenoxyethanol and methyldibromo glutaronitrile (MDGN), in a 4:1 ratio. Contact allergy to it has been increasing in Europe and the USA since its introduction in the mid-1980s and 1990, respectively (1–4). The allergen in EuxylA K400 is virtually always MDGN (5–7) and sensitization is most commonly acquired through exposure to cosmetics and moistened toilet tissue. Less common sources include latex paints and emulsions, adhesives, liquid detergents and metalworking fluids.

Sensitization to cocamidopropylbetaine: an 8‐year review

EuxylAK400 is a biocide containing 2 active ingredients, phenoxyethanol and methyldibromo glutaronitrile (MDGN), in a 4:1 ratio. Contact allergy to it has been increasing in Europe and the USA since its introduction in the mid-1980s and 1990, respectively (1–4). The allergen in EuxylA K400 is virtually always MDGN (5–7) and sensitization is most commonly acquired through exposure to cosmetics and moistened toilet tissue. Less common sources include latex paints and emulsions, adhesives, liquid detergents and metalworking fluids.

Contact allergy to PVP/eicosene copolymer.

Case Report A 32-year-old woman presented with 3 episodes of facial eczema, closely related to the use of a particular sunblock. Patch testing to the standard and a facial series, as well as her own sunblock, showed a ππ reaction to sunblock alone at 2 and 4 days. Photopatch testing was negative. Ingredient testing of the sunblock showed a ππ reaction to polyvinylpyrrolidone (PVP)/eicosene copolymer (10% pet.). 20 control patients tested to this ingredient were negative.