What are immediate vs delayed reactions?

• Classification of drug induced cutaneous reaction according to timing: • Immediate reactions: occur less than 1h of the last administered dose: urticaria, angioedema, anaphylaxis • Delayed reactions: occur more than 1h but usually more than 6h and occasionally weeks to months after the start of administration: Exanthematous eruption, FDE, SJS, TEN, vasculitis