Allergy season is in and I simply cannot live without the medication.

I use Claritin, which is non-drowsy.

But what kind of effect does it have on my physical performance? It doesn't appear to list any side effects.

Try it and let us know. Seriously.

You may be the one who finds out for other allergy suffering cyclists.

(The commercial I've seen on Claritin depicts a lady off-road cyclist who is happy to ride again...)

I was given Claritin once but stopped after one usage because the side effects were too weird. Unusual anxiety and energy and a really weird feeling, like a diet pill. No way I'd ride in such a condition. It may work for others but not me.

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)

I took Claritin after a huge breakfast and after I had a cup of coffee.

Well, my allergy was gone.

But something felt different. I wasn't feeling normal.

I felt more capable physically for sure. I got this "I can go as hard as I want, as long as I want" feeling.... even though I hadn't eaten or drank for a while.

Not sure if that's good or bad.

I tend to think the stimulated feeling may not be good, since it means you are not really in touch with how tired your body is getting, and you may also suffer from "crashing" afterwards.

However, it may be that the Claritin alone will not produce a stimulating effect if you lay off the caffeine. Also to consider: if it is a form of Claritin as mentioned before, containing
pseudoephedrine, it could be the combination of caffeine and pseudoephedrine causing the stimulant effect. I definitely get that effect from that combination.

The other thing to consider is whether or not you are willing to suffer the allergy symptoms by discontinuing the drug.

Nope!
The suffering is not something I can put up with.

Besides all the sever cold-like symptoms I get because of allergies, I get major fatigue as well.

I took Clartin all season last year and I was fine I guess. I'd think if there were any serious effects it had on athelets, it would probably have a warning or something.

I took Claritin for about 4 days. After 4 days, I got bad nosebleeds. (nosebleeds while on a bike ride are not fun)

How I felt while taking Claritin was similiar to how I feel when I take any sinus medication; however, since I have not taken any sinus medication since October, I forget how it feels.

I used to live off of sinus medication. I actually built up a tolerance to Benedril. What helped me was a air filter in my bedroom. Even though I am only in the bedroom for 8 hours, it runs constantly at low speed. Now, most days I don't need sinus medication. If I ever have a bad allergy day, I can now get by with only a 1/2 dose of Walmart brand sinus medication. Severe days require a full dose, but those are only days that I mow, rake, or bale hay.