Comprehensive Patch Testing Effective in Allergic Contact Dermatitis Management

Erin M. Warshaw, MD, MS

New data suggested that comprehensive patch testing with more than 70 allergens, including supplemental series and personal and work materials, was necessary for proper identification of allergens as well as the successful management of allergic contact dermatitis.

Epicutaneous patch testing had been cited as an important tool for the investigation of allergic contact dermatitis, though screening series are often not comprehensive.

Despite larger screening series being able to identify more allergens in patients, most studies have reported only percentages of positive allergens.

Proportions of patients with clinically relevant reactions to supplemental allergens/substances had been reported occasionally in groups such as the North American Contact Dermatitis Group (NACDG). However, details are sparse.

As such, an investigative team led by Erin M. Warshaw, MD, MS, Park Nicollet Contact Dermatitis Clinic, Minnesota, described specific factors of patients with allergic contact dermatitis, in addition to sources of supplemental allergens and their association with occupation.

The Methods

Warshaw and colleagues utilized a 17-year, retrospective cross-sectional analysis of NACDG data from multiple centers in North America. The analysis began on January 1,2001 and concluded on December 31, 2018.

The NACDG screening series consisted of 65 to 70 allergens that changed slightly in composition every 2 years, and additionally supplemental patch tests were chosen based on clinical and occupational history.

A total of 43,417 patients with dermatitis were included in the study, all of whom underwent patch testing to the NACDG screening series in a standardized manner with 65 to 70 allergens and supplemental allergens.

Methods of patch testing, grading of reactions, and recording of data were performed according to the NACDG protocol. The presence of at least 1 currently relevant supplemental allergen/substance was also recorded in addition to grading reactions to allergens on the NACDG screening series.

Reactions to supplemental allergens/substances with past or unknown clinical relevance were not recorded.

The Findings

Of the total number of patients included in the study, 9507 (21.9%) participants had 1 or more currently relevant reactions to a supplemental allergen/substance.

Additionally, a mean of 27.8% of supplement- positive patients (n = 1128) had no currently relevant reactions to a 65-allergen series (2001-2008) compared with 24.5% (n = 1319) to a 70-allergen series (2009-2018).

Of 30,313 patients with positive reactions to 1 or more screening and/or supplemental allergen, 20,806 individuals (68.6%) had positive reactions solely to NACDG screening series allergens, while 2447 (8.1%) had reactions that were positive to only a supplemental allergen/substance, and 7060 (23.3%) had positive reactions to both.

Warshaw and colleagues reported that a majority of supplemental-positive patients were women (69.5%), a percentage that was consistent with a 2013 study on personal care product usage.

Additionally, most personal care product-related contact allergy affected the face and hands, which were the most frequently involved sites of dermatitis in the present cohort.

Sources of supplemental allergens were commonly personal care products such as hair care products and cosmetics. Reactions to allergens in clothing/apparel as well as footwear were also included.

Overall, investigators concluded that, based on exposure and occupational history, comprehensive patch testing included testing not just supplemental allergens but personal care products and workplace materials as well.

“These results suggest that comprehensive patch testing would be useful for the diagnosis and management of contact allergy,” the team wrote.

The study, “Importance of Supplemental Patch Testing Beyond a Screening Series for Patients With Dermatitis The North American Contact Dermatitis Group Experience,” was published online in JAMA Dermatology.