Don't Believe the Hype
Join Date: Feb 2002
Location: chicagoland area
Bikes: 1999 Steelman SR525, 2002 Lightspeed Ultimate, 1988 Trek 830, 2008 Scott Addict
Claritin really has little side effects whatsoever. Claritin alone is just a non-sedating antihistamine - the only side effects are the drying of the sinus that occurs. Sometimes you can can get a drying of the eyes (tear ducts) or constipation from drying of the GI tract. Heck, even Benadryl over the counter is stronger than Claritin but is really sedating....
The side effects mentioned by other posters is probably due to the Claritin-D, which has a sustained release (sometime unpredictable release) of the active ingredient in sudafed. The 24 hour Claritin-D, for example has 240mg sudafed that is supposed to release over 24 hr period, but it depends on how you take it (with hot coffee, cold water, carbonated beverage, empty stomach, full stomach, with caffeine, etc)