Allergic Contact Dermatitis Evaluated Among Patients Referred for Patch Testing

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There is no increase in the presence of allergic contact dermatitis among individuals with atopic dermatitis who were referred for patch testing, according to new findings, as these patients’ profiles were identified as comparable to non-atopic dermatitis populations.¹

This study was designed with the aim of identifying allergic contact dermatitis profile differences between those with and without the skin condition of atopic dermatitis, also known as eczema, among patients referred for patch testing. The study was done in Spain and a secondary goal was to determine the level of sensitization to standard Spanish contact allergens within both cohorts.

This research was authored in part by P. Chicharro at the Academia Española de Dermatologia y Venereología in Madrid, Spain. Chicharro et al. highlighted the fact that prior research had demonstrated mixed findings regarding allergic contact dermatitis.²

“There are no published data on the association between contact sensitisation and (atopic dermatitis) in Spanish clinics patching patients with suspected contact allergies,” Chicharro and colleagues wrote. “In this study, our primary aim was to identify differences in patch testing outcomes between patients with and without (atopic dermatitis) among those referred for patch testing, using data from the Spanish Registry of Research in Contact Dermatitis and Cutaneous Allergy (REIDAC).”¹

Background and Design

The investigators implemented data from the national registry REIDAC, a registry which is designed to prospectively gather information on all consecutive patients who have been given patch testing in participating dermatology clinics within Spain. They used a multi-center, prospective, observational study design, including REIDAC data from the period of January 2018 - June 2020.

There were 2 cohorts into which the research team divided participants: subjects that were shown to have a personal history, final diagnosis, or secondary diagnosis of atopic dermatitis (titled the ‘AD group’) and individuals that did not have a history of the skin condition (known as the ‘non-AD group’).

Subjects were determined to have met the eczema criteria provided they either previously had a diagnosis of the condition or that they met the criteria during their consultation. Patch-testing occurred among all subjects with the Spanish standard series, with investigators gathering the allergens from allergEAZE, Chemotechnique, and True-Test, depending on their availability within each center.

Two readings were done for each patch test, with the research team considering the relevance of the findings following their clinical examination and later assessment of previous exposure histories among participants. The team presumed current relevance provided that sensitization could explain or contribute to the condition.

Both the nature and the relevance of the reaction were identified by the investigators. They also reported on subjects’ gender, rhino-conjunctivitis, potential sources of exposure within work areas, background of eczema, sites impacted, asthma, generalized involvement, and duration of subjects’ symptoms.

The Chi-squared test was used for an analysis in which the team compared the AD and non-AD cohorts. Logistic regression with odds ratios (OR) and 95% intervals was also carried out by the investigators to assess the link between eczema and positive patch test reactions.

Trial Findings

Overall, the research team concluded that among the 5055 patients who were evaluated after patch testing, 23% were shown to have a history or final diagnosis of atopic dermatitis. The team determined that at least a single positive reaction was observed among 40% of those in the AD group and among 48% of those in the non-AD group.

The most common positive reactions observed by the investigators during the study among both groups were allergies to methylchloroisothiazolinone/methylisothiazolinone, nickel sulfate, and cobalt chloride. The age-adjusted OR for sensitization to nickel sulfate was noted by the team as 0.72 (95% CI: 0.61–0.86). This suggested there was a diminished likelihood of sensitization among those with eczema versus those without.

“(Atopic dermatitis) patients suspected of having ACD should be patched considering exposure to potentially relevant allergens, including fragrances, preservatives, corticosteroids and occupational and personal exposures,” they wrote. “The selection of allergens for testing should be the same in patients with (atopic dermatitis) as in those without (atopic dermatitis).”

References

1. ^{Chicharro P, Munera-Campos M, Zaragoza-Ninet V, et al. Allergic contact dermatitis in adults with and without atopic dermatitis: Evaluation of the Spanish Contact Dermatitis Registry (REIDAC). Contact Dermatitis. 2024; 1-8. doi:10.1111/cod.14672.}
2. ^{Simonsen AB, Johansen JD, Deleuran M, Mortz CG, Sommerlund M. Contact allergy in children with atopic dermatitis: a systematic review. Br J Dermatol. 2017; 177: 395-405.}