Cold or Allergy? How to Tell the Difference


Sneezing, stuffy head, runny nose can all be signs of colds and allergies; how to distinguish


Last month, I developed what I thought was a head cold—that sneezing, drippy nose, stuffed-up feeling—until it didn't go away, or rather went away and then came back again and again. Maybe it's allergies, friends told me, except I've never had them before. Then again, people can develop allergies at any point in their lives, and studies suggest that as many as 40 percent of Americans are sufferers. So I asked Mayo Clinic allergy specialist Hirihito Kita to help me distinguish a cold from an allergy.

Unfortunately, he tells me, you can't always know for certain, since the two share symptoms: sneezing, runny nose, congestion, and fatigue. While colds are caused by hundreds of different viruses, allergies are triggered by harmless substances, like ragweed, pollen, or cat dander, that your body mistakes for a threatening invader. In either case, symptoms result from your immune system's response to the interloper; the release of the chemical histamine, for example, causes your sinuses to swell, your nose to run, and sneezing.

In terms of distinguishing between the two, the National Institute of Allergy and Infectious Diseases has this chart which provides some clues. Colds last only one to two weeks, commonly cause cough, sore throat, and sometimes body aches and fever, but not itchy, watery eyes. Allergies can last for a month or more, commonly cause itchy eyes, and don't cause fevers or body aches; plus, they tend to cause coughing only in those who have asthma, says Kita.

How does he tell one from the other when he feels ill? "If my sneezing turns into a cough after two or three days, then I know it's a cold. If my sneezing continues without other symptoms for a week, then I know it's an allergy," says Kita. He also examines the tissue after blowing his nose. If the mucus turns thick and yellow after a few days of symptoms, it's likely a cold; mucus that remains thin and clear usually signals an allergy.

In terms of treating your own symptoms, you can't do much harm if you mistake a cold for an allergy (or vice versa) since over-the-counter remedies are usually the same for both. Antihistamines like Benadryl, Claritin, or Zyrtec work to dry up your nasal passages and decongestants like Sudafed or Tylenol Sinus help reduce swelling to alleviate that stuffed-up sensation. Of course, any aches or fevers can be eased with a pain reliever like Advil or Tylenol.