Rare. Hives that only occur after taking the medication. Swelling afterwards, coughing, wheezing or shortness of breath.
Very unusual. Allergy to Clarinex (desloratadine) would include hives, itching, rash, shortness of breath, wheezing, and swelling. If you think you may be allergic to clarinex, (desloratadine) you should discontinue it immediately and consult with your doctor or go to the er.
Antihistamines. There are several newer antihistamines that are now over the counter. They all are about the same. Allegra, zyrtec and Claritin (loratadine) to name a few. Try these at suggested dosage. If they don't work, see your doctor.