It’s not always easy to tell, but there are clues, according to the American Academy of Otolaryngology.
Flu, or influenza: The hallmarks of this viral illness are a fever of 102 to 104 degrees Fahrenheit that lasts for three or four days. Nasal discharge is usually thick and whitish or thin and watery. You will probably have a headache and a cough and most likely, muscle aches. You may or may not have a sore throat, nasal congestion and sneezing. You usually do not have facial pain or pressure, itchy eyes or pain in your upper teeth. The misery usually lasts for fewer than 10 days, but fatigue may last longer.
Cold: With this viral illness, you are not as sick. You may or may not have a short-lasting fever, a headache, facial pain or pressure and pain in your upper teeth. You will have a sore throat, cough, nasal congestion, sneezing and some fatigue or weakness. Nasal discharge will be thick and whitish or thin and watery. You won’t have itchy eyes. The illness usually lasts fewer than 10 days.
Allergies: These are triggered not by viruses, but by allergens like dust, mold and pollen in the environment. You won’t have a fever or pain in your upper teeth. But you may have facial pain or pressure and you may have a headache, cough, nasal congestion, fatigue or weakness, and a sore throat. Nasal discharge will be clear, thin and watery. You will have itchy eyes and sneezing. The duration of allergies varies.
Sinusitis: This is an inflammation in the sinuses that can be caused by allergens, viruses or bacteria. You will have facial pain or pressure, a thick, yellow-green nasal discharge and sometimes, a fever. You probably won’t have itchy eyes, but you probably will have a headache and nasal congestion. You may or may not have pain in your upper teeth, bad breath, a cough and sore throat. You may have fatigue or weakness and – this is an important clue – your misery will last more than 10 days.
If the nasal discharge is yellow-green for more than six days, if you’re getting markedly worse or a fever develops later in the illness, you should call a doctor, advises Dr. James Cooley, chief of pediatrics at Wellesley office of Harvard Vanguard Medical Associates. There are anti-viral medications for the flu, including Amantadine, Rimantadine, Zanamivir or Oseltamivir. You should not take antibiotics for a cold or the flu, though these illnesses can develop into bacterial infections, for which antibiotics are appropriate.