Will taking an extra dose of allergy medicine help me/hurt me?

It might do a little harm, but everyone’s bodies are different, and therefore handle medication differently. It may not have any effect on you at all, good or bad. Meaning, it might make you groggy, or it might not improve your allergies at all beyond what you experience with the 1 pill. However, that being said, Claritin does nothing for my allergies—you might consider a change of medication. Benadryl is the only one that seems to work for me, but once I took a pill too many and knocked myself out cold for 9 hours.

I agree with breanne. I would change your medication. Zyrtec (now over the counter) works much better for me with cat allergies and itchy eyes.

Benjamin, I might suggest a different route. Studies have shown that intranasal steroids (like Flonase) work much better at preventing the symptoms of seasonal allergies than antihistamines. Granted, you need a prescription, but that is a small price to pay (assuming you have insurance). Claritin, Allegra, Zyrtec all work at treating the symptoms, but an ounce of prevention is worth a pound of cure. If you are still having issues, and cannot take intranasal steroids, then I agree that Zyrtec is most effective (but also most sedating). You might also try taking Benadryl at night, since you are going to be sleeping anyway. That way you sleep better and don’t wake up with itchy eyes and that “beat up” feeling in the morning.