Well, if it's not allergies, then the antihistamine will do you no good. Only the decongestant will be of any use.

Take heart, though - if it's just a plugged-up nose that distresses you, you probably don't have allergies. Any of us allergics can tell you that commerical hawking the product for "nasal allergies" is pretty misleading - allergies attack your nose, eyes, throat, ears, skin, and in those of us who are also asthmatic - the bronchi!

Strangely enough, as bad as my allergies are, I almost never suffer any sinus distress!