What is a common side effect associated with antihistamines?

Antihistamines are commonly associated with urinary retention due to their anticholinergic properties. These medications block histamine receptors, which are involved in various physiological functions, including the regulation of smooth muscle tone in the bladder. The anticholinergic effects can result in decreased bladder contractions, leading to difficulty in urination or urinary retention.

In contrast, hypotension is not a typical side effect of antihistamines, as they are more likely to cause sedation and drowsiness rather than lowering blood pressure. Diarrhea is also not a common side effect; instead, antihistamines may actually cause constipation in some patients. Increased salivation is typically not associated with antihistamines; in fact, their anticholinergic actions can lead to dry mouth in certain individuals. Thus, the side effect of urinary retention stands out as a well-known adverse effect in this class of medications.