What class of antihistamines does diphenhydramine belong to?

Diphenhydramine belongs to the first generation of antihistamines. This classification refers to antihistamines that were developed earlier and are known for their ability to cross the blood-brain barrier, leading to sedative effects as a common side effect. First-generation antihistamines, like diphenhydramine, are often used for allergic reactions as well as for their sedative properties.

In contrast, second-generation antihistamines are specifically designed to minimize sedation by not crossing the blood-brain barrier as readily, allowing them to effectively reduce allergy symptoms with less drowsiness. Non-sedating antihistamines are primarily associated with second-generation medications, which again distinguishes them from first-generation drugs such as diphenhydramine. Intranasal refers to a route of administration rather than a classification based on the generation of the medication and does not characterize diphenhydramine’s category.