The question frequently arises whether patch testing is a reliable procedure during treatment with systemic corticosteroids. To further explore possible suppression of patch-test reactions during systemic corticosteroid treatment, 18 young, healthy individuals who had a history of Rhus dermatitis were patch-tested with various dilutions of Rhus antigen before, during, and (in ten subjects) after oral administration of 40 mg of prednisone daily for seven days. Results showed definite and significant diminution of reactions during treatment with prednisone, although rarely complete disappearance. Since such decreased reactions may be incorrectly interpreted as mild irritant reactions or reactions to occlusion and thus read as negative, patch testing should be deferred until the patient is no longer receiving high doses of systemic corticosteroids.
Condie MW, Adams RM. Influence of Oral Prednisone on Patch-Test Reactions to Rhus Antigen. Arch Dermatol. 1973;107(4):540-543. doi:10.1001/archderm.1973.01620190016003