keyetv.com in Austin, TX reports that decongestants may aggravate symptoms in men with enlarged prostates.

“If a man has an enlarged prostate that is already causing him problems, the further constriction that the medicine causes on those alpha nerve terminals in the bladder and the prostate area, will cause it to further clamp down,” said Urologist Dr. Koushik Shaw with the Austin Diagnostic Clinic.

Men with enlarged prostates should avoid taking allergy medicines with decongestants. Sometimes it will list "decongestant" on the box, but you should check the ingredients.

If the label says psudefed, pseudoephedrine or ephedrine, Dr. Shaw says avoid it. Claritin D, for instance, is not okay, but Claritin is.