Knowing the difference guides the selection of medications. And to complicate a course of treatment, colds can make irritated noses far more susceptible to allergic reactions from pollen of trees, weeds and flowers, said Dr. Gillian Shepherd of the New York Presbyterian Hospital. Generally, cold medications are decongestants. Their job is to shrink swollen membranes in the nose and make breathing easier. Antihistamines typically are taken for allergies.
Some medications combine the two.
A mild analgesic is often blended into the product. Itchiness is frequent with allergies, uncommon with colds. Allergies almost never cause fevers. It may be seasonal or year round and can be diagnosed by history, physical exam and allergen skin prick testing. Perennial rhinitis is caused by an allergic reaction to nonseasonal causes such as skin flakes and hairs of household pets, house dust mites, feathers, molds and pillow stuffings.