This is my second favorite allergy medicine for the spring when the pollen hits me hard. The national brand of Zyrtec costs a little more so I just bought this one instead. My allergies can get so bad in the spring that even with a 24-hour allergy pill, I'll have to take a Benadryl at night to relieve symptoms. I rarely have to do that with the Wal-Zyr. I don't wait until symptoms begin before taking it, though, so I am not sure if it's fast acting or not. I try to get this stuff into my body at least a week before the allergies begin because once I start sneezing and get a runny nose, it's hard to contain. Wal-Zyr stops the sneezing, runny nose, water eyes but I still get itchy eyes. Not as bad as if I didn't take the meds, though. I think allergy meds are still affordable when compared to prescriptions, especially if you buy the store brands. Now, for the reason this is my second favorite and not my first. It tends to make me jittery. Last spring I stopped using it for a few days and used another allergy med because the Wal-Zyr was making me feel like I'd been consuming too much caffeine. Sometimes you just have to weigh the pros against the cons.