Predicting which medication classes interfere with allergy skin testing

Medications often interfere with allergy skin test interpretation. This study was performed to determine which medications interfere with allergy skin tests. We retrospectively reviewed skin-prick test results from patients who had discontinued H₁-antagonists, tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), selective norepinephrine reuptake inhibitors (SNRIs), benzodiazepines, atypical antidepressants, antipsychotics, hypnotics, sedatives, proton pump inhibitors (PPIs), and H ₂-antagonists between 0 and 7 days before allergy skin testing. Ninety-seven subjects had taken second-generation H₁-antihistamines within 7 days of skin testing; all patients who had stopped 3 days before testing had positive histamine controls. Two hundred sixty-eight skin tests performed on patients taking a single medication of interest showed that patients had the following percentages of a positive histamine control: TCAs, 56.5%; SNRIs, 100%; H₂-blockers, 100%; SSRIs, 97%; PPIs, 97%; benzodiazepines, 85.7%; and atypical antidepressants/sedatives, 92.6%. The 580 patients taking multiple medications of interest showed that the odds ratio and 95% confidence intervals of a negative histamine test for patients taking TCAs were 6.33 (2.11-20.5), for H₁-blockers were 4.95 (1.78-15.1), for benzodiazepines were 5.01 (1.72-15.80), for atypical antidepressants/sedatives were 3.11 (1.09-9.61), and for H₂-blockers were 2.91 (0.97-9.37). The odds of a negative histamine test for SSRIs, SNRIs, or PPIs were not significantly increased. SSRIs, SNRIs, and PPIs are unlikely to interfere with skin testing. TCAs, H₁-blockers, benzodiazepines, quetiapine, and mirtazapine should be discontinued temporarily if clinically able. H ₂-antagonists, bupropion, eszopiclone, trazodone, or zolpidem showed minimal interference with immediate hypersensitivity skin test histamine response.