The literature on positive patch test results in drug reaction with eosinophilia and systemic symptoms (DRESS) is reviewed. One hundred and five drugs were identified that have together caused 536 positive patch tests in 437 DRESS patients. By far, the most reactions (n = 145) were caused by carbamazepine, followed by amoxicillin, isoniazid, phenytoin, ethambutol, fluindione, phenobarbital, rifampicin, and ceftriaxone; 43 drugs each caused a single case only. The drug classes causing the highest number of reactions were anticonvulsants (39%), beta-lactam antibiotics (20%), antituberculosis agents (11%), non-beta-lactam antibiotics (6%), and iodinated contrast media (5%). The sensitivity of patch testing (percentage of positive reactions) is high for anticonvulsants (notably carbamazepine), beta-lactam antibiotics (notably amoxicillin), and, possibly, iodinated contrast media. Allopurinol and sulfasalazine frequently cause DRESS but never give positive patch tests. Patch testing in DRESS appears to be safe, although mild recurrence of DRESS symptoms, mostly skin reactions, may not be rare. Multiple drug hypersensitivity was found to occur in 16% of all patients, but it is argued that the true frequency is higher. Clinical aspects of DRESS, including diagnosing the disease and identifying culprit drugs (patch tests, intradermal tests, in vitro tests, challenge tests) are also provided, emphasizing the role of patch testing.