Antihistamines block the H1 receptor that histamine uses to produce the sneezing, itching, runny nose and hives of an allergic reaction. The second-generation drugs were designed not to cross into the brain, which is why they are far less sedating than older options such as diphenhydramine — though they are not all equally non-drowsy, and that is the main thing that separates them.
Class descriptions are written by the Priya Life Science editorial team. Individual drug pages combine that summary with live label, approval, manufacturer and shortage data from the U.S. FDA via the openFDA API. This page is general information and is not medical advice — it is not exhaustive, drugs within a class are not automatically interchangeable, and approvals and brand names differ between the US, EU/Ireland (EMA/HPRA) and other regions. Always consult the official prescribing information and your clinician or pharmacist. Related: Drug Shortages Tracker · FDA Approvals · All drug comparisons