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.
The facts on this page are pulled directly from official U.S. FDA datasets — they are not written from memory. Each field below names the dataset it came from, so you can check it yourself.
Plain-English summaries and drug-class explainers are written and reviewed by the Priya Life Science editorial team, led by Sreepriya Prasannan (MSc Digital Transformation of Life Sciences (Innopharma Education / Griffith College); MSc & BSc Botany). Data is retrieved automatically from the sources above and cross-checked with AI-assisted verification (Anthropic's Claude) — brand and generic names are matched against the exact FDA product record so that a combination product or a different formulation cannot be mistaken for the drug on this page. An editor reviews the result before publication. We describe this in full in our editorial standards and corrections policy. The FDA data on this page was last retrieved on 9 Aug 2026.