What are some common side effects of antihistamines?

Antihistamines are commonly used to alleviate allergic symptoms by blocking histamine receptors in the body. One of the most notable side effects associated with many antihistamines, particularly the older first-generation ones, is drowsiness. This sedative effect occurs because these medications can cross the blood-brain barrier and influence neurotransmitter activity related to sleep and wakefulness.

Moreover, antihistamines often lead to dry mouth due to their anticholinergic properties, which reduce saliva production. This is another characteristic effect of these medications that can cause discomfort but is a common occurrence with their use.

While nausea and vomiting, rash and itching, as well as pain and swelling might be observed in some patients, these reactions are not typically classified as common side effects of antihistamines. Instead, drowsiness and dry mouth stand out as hallmark side effects, making the selection of drowsiness and dry mouth the most accurate representation of what can generally be expected when taking antihistamines.