What's the Difference Between First-Generation and Second-Generation Antihistamines? - WebMD
Antihistamines are a class of drugs that help to treat the symptoms of various allergies. The main difference between first-generation and second-generation antihistamines is that the latter do not cause sleepiness and are considered safer because they interact better with other medications. What Are Antihistamines Used For? Antihistamines are medications that block chemicals in the body called histamines. Histamines are the chemical that gets released after you are exposed to something you are allergic to. They cause the symptoms of an allergic reaction, like: Itchiness Hives Runny nose Itchy eyes Sneezing Insomnia Nausea Vomiting Fatigue There are two different types of histamines: H-1 receptor antagonists and H-2 receptor antagonists. Typically, antihistamines that treat H-2 receptor antagonists treat gastrointestinal symptoms. Both first-generation and second-generation antihistamines treat H-1 receptor antagonists. H-1 receptor antagonists treat: What Are First-Generatio...