Anaphylaxis resulting from patch testing is very rare, according to new research presented at the American Contact Dermatitis Society (ACDS) 2022 Annual Meeting, held in Boston. The reaction was estimated to occur in fewer than 1 in 100,000 patients.
While anaphylaxis is listed as a potential risk of patch testing, there were previously no data indicating how often these events occur, said Karishma Daftary, a medical student at the University of Louisville School of Medicine, Kentucky, and a visiting predoctoral research fellow in Northwestern University School of Medicine’s Department of Dermatology in Chicago. She presented the research at the March 24th conference.
“We were curious to see how common this is,” she said in an interview with Medscape Medical News. “Have most patch testers had an experience like this, or is it more rare?”
To find out, Daftary and colleagues invited 35 expert patch testing dermatologists from the United States and Canada to complete a survey asking participants about their years of experience patch testing, the average number of patients for whom they conduct patch tests each year, and any history of patients developing anaphylaxis following patch testing. To distinguish these events from panic attacks, which can sometimes have anaphylaxis-like symptoms, cases only qualified if a patient had difficulty breathing, experienced hypotension, and was in need of additional medical care (such as an EpiPen or a transfer to the emergency department).
There were 27 respondents to the survey, and collectively, they had conducted patch tests for 201,720 patients over their careers. On average, the physicians had been patching testing for an average of 21 years and had tested about 343 patients per year. Just two cases of anaphylaxis were reported by this cohort, both caused by fragrance. Both patients had a history of anaphylactic symptoms prior to undergoing patch testing, Daftary said. Using these data, she and her colleagues estimated that the rate of anaphylaxis in patch testing was 1 in 100,860 tests.
The group also conducted a literature review to identify cases of anaphylaxis and immediate hypersensitivity following patch testing. The reports were published up to March 2021. To be included in the review, all reports needed to include the allergens in the American Contact Dermatitis Society 2017 Core Allergan Series.
From the literature review, the research group identified 495 cases of immediate hypersensitivity reactions from patch testing. Only five of these involved anaphylaxis. Those patients all had a history of anaphylaxis. Their reactions were caused by the allergens chloroxylenol, chlorocresol, cinnamic aldehyde, or mixed dialkyl thioureas. The remaining 490 cases were urticarial reactions and were most commonly caused by balsam of Peru (197), cinnamic aldehyde (28), and fragrance mix 1 and 2 (115).
These findings are “reassuring” and confirm what dermatologists usually see in practice: “It’s very uncommon to encounter anaphylaxis in patch testing,” Ari Goldminz, MD, the director of the contact dermatitis program at Brigham and Women’s Hospital in Boston, told Medscape. (Goldminz is chair of the ACDS Program Committee and said all opinions are his own.) He was not involved with the study.
Although it is rare that a patient may have this reaction following patch testing, dermatologists should ask patients, if they don’t already know, about any history of hypersensitivity reactions, including anaphylaxis, prior to testing, Daftary said, and they should develop an office protocol in case a patient does have anaphylaxis-like symptoms. “As with any emergency situation, it’s important to have a plan in place,” Goldminz added.
Patch testing for people with a history of anaphylaxis should be considered on a “case by case basis,” Goldminz said. In his clinic, he also conducts contact urticaria tests, which can at times cause more severe allergic symptoms, he noted. “It’s always important to assess the utility of patch testing for each patient,” he said. For more complex cases, one should “think through beforehand what the most helpful test would be.”
Daftary and Goldminz reported no relevant financial relationships.
American Contact Dermatitis Society (ACDS) 2022 Annual Meeting.
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