Suggest Treatment For Allergic Reaction To Clariton

Hi, my question is about an allergic reaction to clariton. I've been taking it for about a week and was not aware that the symptoms I've been having this week align with those of an allergic reaction to the drug. My question is, is it possible for me to have one, seeing how I have never been allergic to this drug in the past, or any drug for that matter?