What is a primary effect of diphenhydramine that differentiates it from non-sedating antihistamines?

Diphenhydramine is an antihistamine known for its sedative properties due to its ability to cross the blood-brain barrier and exert effects on the central nervous system. This sedating effect is a key differentiator from non-sedating antihistamines, which are designed to minimize drowsiness and sedation.

When comparing diphenhydramine with non-sedating antihistamines, the likelihood of causing drowsiness is significantly higher with diphenhydramine. Patients taking diphenhydramine may experience sedation as a common side effect, making it less favorable for individuals who need to remain alert, such as when driving or operating heavy machinery.

In contrast, non-sedating antihistamines like loratadine or cetirizine are formulated to provide allergy relief without the sedating effects, thereby making them preferable for daytime use or for individuals who need to avoid drowsiness.

While diphenhydramine may be effective for allergy symptoms, the primary impact that sets it apart in this context is its propensity to cause drowsiness, which is critical for users to consider when selecting an appropriate antihistamine for their needs.