Topical steroid allergy copositivity ‘rare,’ ‘variable’ among patients with various rashes

Copositivity for allergies to multiple topical corticosteroid products was rare in a large group of patients with various rashes, according to a study.

“Many patients use topical corticosteroids to treat various rashes in dermatology, and some patients develop contact dermatitis to the corticosteroid itself,” Yul W. Yang, MD, PhD, of the department of dermatology at the Mayo Clinic in Scottsdale, Arizona, told Healio. “Here, we analyzed our institution’s patch test data to better understand corticosteroid allergy.”

Many patients who are allergic to one topical corticosteroid are also allergic to other corticosteroids, according to Yang.

The researchers suggested that classification models to predict copositivity to corticosteroid allergies and guide allergen avoidance may be useful.

“There is simply an abundance of available corticosteroids, too many to patch test each one,” Yang said. “As we cannot test to each and every steroid, previous research has described two different classification models that have guided the selection of a few screening corticosteroids in patch testing.

The current qualitative study included a retrospective analysis of Mayo Clinic Contact Dermatitis Group patch test data for 49,472 tests from 5,637 patients assessed between 2010 and 2019. Eighteen corticosteroids underwent analysis.

Copositivity rates between corticosteroids served as the primary outcome measure. The researchers also aimed to determine overall copositivity patterns assessed against known steroid classes using previous classification models, according to the findings.

“Here, we reviewed the past 10 years of Mayo Clinic topical corticosteroid patch test data and used unsupervised hierarchical clustering to compare our data to the prior corticosteroid classification models,” Yang said.

Results showed overall patch test positivity rates between 0.3% and 4.7%.

Fluocinonide positivity corresponded with the highest copositivity rate with other drugs in the class, at a mean of 50.7% (standard deviation [SD], 26.1%).

The lowest allergy positivity rates were observed for tixocortol-21-pivalate 0.1% and tixocortol-21-pivalate 1%. These drugs also carried the lowest copositivity rates at 4.1% (SD, 1.7%) for the 0.1% formulation and 3.6% (SD, 1.4%) for the 1% formulation.

Importantly, hierarchical clustering showed patterns that were not consistent with prior corticosteroid classification models, according to the researchers.

“We were surprised that our real-life clustering analysis did not match either previously defined corticosteroid classification model,” Yang said.

The researchers concluded that copositivity rates were “variable” between drugs in the class, with “rare” overall patch test positivity for allergies to corticosteroids.

“When patch testing for potential corticosteroid allergy, we feel that dermatologists should consider testing for clinically relevant corticosteroids, rather than relying solely on screening corticosteroids,” Yang said.