Background: Few data on the effect of antihistamines on patch test results in Chinese patients are currently available.
Objectives: To evaluate the effect of desloratadine on patch test reactions.
Methods: Patients known to have at least one strongly positive (+ +) test with an allergen were re-patch tested after 14 to 70 days (average time interval 26.3 days) of administering oral desloratadine 5 mg twice a day for 5 days before and during the test. Patch testing was performed with the previously recognized allergen according to the guidelines of the ICDRG. The -to + + + system was converted into numeric values (0, 1, 2, 3, 4) for statistic evaluation.
Results: Of the 58 chambers (47 patients), which were all strongly positive (+ +) during the 1st patch test, the situation was unchanged in 51 chambers; 4 + reactions and 2 + + + reactions were observed; and 1 chamber was negative. There was no statistically significant difference when comparing the scores of the 1st assessment with those of the 2nd (p = 0.206). If the patch test reaction of the patient who dropped out of the trial had changed from strongly positive (+ +) to negative, there would still have been no statistically significant difference between the score of the 1st assessment with those of the 2nd ( p = 0.107).
Conclusions: The reaction of a patch test is not hampered by doubling dose of desloratadine. The anti-inflammatory effects of desloratadine on patch test reaction may be limited.