How To Figure Out If You Have A Cold, A Flu, Or Allergies

BI Answers: How can you tell if you have a cold, a flu, or allergies?

When you wake up sick, with a scratchy throat, a stuffy nose, and a vague constellation of other miserable symptoms, it's important to figure out exactly what's ailing you.

Is it just hay fever, or are you contagious? Should you suffer through the work day with your cold, or are you about to unleash a nasty strain of flu on your whole office?

There are a few key strategies for determining the difference between three of the most common causes of respiratory distress: the cold, the flu, and seasonal allergies. We sorted through the research and talked to Dr. Robert Wergin, the president of the American Academy of Family Physicians, who has seen plenty of of sneezing, coughing patients since he began practicing medicine 34 years ago.

A Three-Step Plan

First, think about the time of year. In the fall, three quarters of all circulating viruses are rhinoviruses, the most common cause of colds. In the spring and summer, when colds still crop up but respiratory illnesses are less widespread, seasonal allergies run wild. (If you get allergies regularly, pay attention to what month they seem to strike each year.) From late fall all the way through winter, meanwhile, you should be on the lookout for the flu, or influenza. Flu season peaks between November and January.

Second, take stock of your symptoms. A flu is, in general, more severe than a cold, and it is usually accompanied by a fever (100F+), an achey body, and what the NIH calls "extreme exhaustion." With a flu, "symptoms such as fever, body aches, extreme tiredness, and dry cough are more common and intense,"  explains the Centers for Disease Control and Prevention. A flu can also cause serious complications like pneumonia. 

People with colds, meanwhile, are more likely to experience stuffy or runny noses. And seasonal allergies, Wergin explains, often come with itchy eyes and nose - and, subsequently, sneezing - though sufferers can also develop a sore throat from a post-nasal drip.

Third, wait and see - the duration of your illness matters. Your allergies will stick around as long as whatever allergen triggers them is still in the air, which can be more than a month. A bad flu can sometimes last a little longer than a cold, with symptoms like fatigue persisting up to three weeks.

Jonathan Ernst/ReutersWhether it's a cold or a flu, try not to pass it on.

What To Do Next

"If you have standard symptoms and you're managing okay at home," then getting plenty of rest, fluids, and using over-the-counter medications as needed is probably fine, Wergin says. Just try to avoid giving it to other people. "If it goes beyond 5-7 days, you ought to be checked by a doctor." (People who are pregnant or have chronic health conditions should probably check in with their doctor sooner.)

With some cases of respiratory discomfort, it's hard to tell exactly what's going on without conducting a test. The CDC says definitively figuring out the difference between a cold and a flu "based on symptoms alone" can be "difficult (or even impossible)." A team of Australian researchers conceded the same point, noting that "many viruses are known to cause clinical illness that is difficult to distinguish from influenza."

While antiviral medications like Tamiflu can help fight a flu if you get to your doctor early, "the best treatment of influenza is not to get it," Wergin says. "Get a flu shot."

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