Second-generation antihistamines have shorter half-lives and require more frequent dosing compared to first-generation antihistamines.

First-generation antihistamines block both histamine and muscarinic receptors, while second-generation antihistamines primarily block histamine receptors.

First-generation antihistamines are less likely to cause sedation compared to second-generation antihistamines.

Second-generation antihistamines cross the blood-brain barrier, causing significant central nervous system effects.