There are a couple of kinds of antihistamines now, the old kind and the new and improved kind. The new kind only release enough histamine blocking drug prevent you from sneezing and wheezing (or whatever else you allergy sufferers do). The old kind, which are much more fun if you ask me, release enough histamine blocking drug to permeate every single cell in your body.

I can hear you now saying, isn't that better? Doesn't more drug mean less sniffles? Well, yeah, but your brain relies on histamine to function properly, so the old kind of pills will thoroughly zonk you. If you're driving, take the new ones. If you're looking for a little more entertainment during the allergy season and you're not an air traffic controller or anything, then give the old ones a try.

Brand names of the new kind: Claritin-D, Allegra, etc.
Brand names of the old kind: Whatever's at Wallgreen's.