Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome is a rare but potentially life-threatening hypersensitivity reaction to certain medications, including allopurinol (a xanthine oxidase inhibitor), antiepileptics (e.g., phenytoin, carbamazepine), and antibiotics (e.g., vancomycin). This evidence concerns the gene XDH and Increased total eosinophil count.