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The Difference Between Cold, Flu & Allergies Explained

Published:
Jan 25, 2021
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Updated:
Jun 4, 2021
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Contributor:
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5 minutes

Medically reviewed by

Devon Scoble
Devon ScobleDevon Scoble
Health Writer & Editor
Devon is a health trends writer and editor. Her personal experience with autoimmune disorders fuels her passion for producing stories that help readers understand—and ideally, heal—what ails them.
Learn about our content process
Ivor A. Emanuel, MD
Ivor A. Emanuel, MD
Allergy & Otolaryngology Doctor
Dr Emanuel is a board-certified otolaryngologist and is considered a national expert in the field of sublingual immunotherapy and allergy blood testing. Dr Emanuel has been in practice for more than 25 years.
Learn about our content process

Colds, allergies, and flu operate differently in the body, even if the misery they cause can share certain characteristics.  

Learn how to identify whether your sniffles and sneezes, aches and pains or scratchy throat and cough symptoms are the result of a cold, flu or allergies so that you can treat them—and, hopefully, beat them.

 

Is it a cold, flu or allergies?

Identifying allergies

Perhaps not surprisingly, seasonal allergy symptoms are, well, seasonal, occurring in spring, summer and fall, when triggers like pollen are in the air. Seasonal allergies can persist, lasting for weeks or months, depending on the specific trigger.

Dr. Ivor Emanuel, M.D. is an allergist and ear, nose and throat specialist, and has published numerous papers on allergy diagnosis and treatment, acute and chronic sinus disease, asthma, and more. He says while allergies and colds share some characteristics, allergies are more likely to cause a stuffy nose than a runny one. Itchy watery eyes are also a clue that you’re probably dealing with an allergy. If your stuffy nose and itchy eyes persist year round, he suggests seeing an allergist to get assessed for a chronic allergy, such as one from dust mites or mold.

Ruling out a cold

Cold symptoms usually start off mild, gradually getting worse before resolving within a week or two¹. And “cold” is really a catch-all term that describes a variety of viruses—but if yours comes with yellow or green mucus and lasts longer than two weeks, it’s probably not one of them.

“There’s no such thing as a three-week cold,” says Dr. Emanuel, so if your symptoms include colorful mucus, or persist longer than two weeks, you should get checked for a bacterial sinus infection.

How to tell if it’s flu

Of the three no-fun-fests on discussion here, flu is the easiest to identify—mainly because it’s just so miserable. The defining characteristic of flu is extreme knock-you-out, drag-you-down exhaustion—not to be confused with allergy fatigue, which isn’t achy and won’t keep you bed-bound. While allergy and cold symptoms can make you feel pretty bad, if you’re struggling to get out of bed alongside other symptoms like chest pain, nasal congestion, sore throat or cough, then it’s likelier flu.

Like colds, flu symptoms typically last one or two weeks. And like allergies, flu has its own season, most often occurring in late fall and winter.

Cold vs allergies vs flu chart

Use this chart to help narrow down your symptoms²³⁴⁵⁶⁷:

 

Symptom
Cold
Seasonal Allergies
Flu

Runny nose

Common

Possible

Possible 

Stuffy nose

Common

Common

Possible

Sneezing

Common

Very Common

Possible

Itchy, watery eyes

Rare

Very Common

Rare

Cough

Common

Possible

Common

Sore throat

Common

Rare

Possible

Fatigue

Possible

Possible

Common

Extreme fatigue

Never

Rare

Common

Fever

Possible

Never

Common

General aches and pains

Possible

Rare

Common

Chills

Possible

Never

Common

Headache

Rare

Rare

Common

Gradual onset

Common

Never

Rare

Quick onset

Rare

Common during allergy season

Common

Treatment

Get plenty of rest and  fluids. You may take decongestants & aspirin or ibuprofen for aches and pains. If symptoms persist beyond 2 weeks, see a doctor.

Avoid allergens. Take antihistamines as needed and as directed by a pharmacist or doctor.

Plenty of rest and fluids. You may take ibuprofen or acetaminophen for pain and to reduce a fever. Consult a doctor if you experience chest pain, shortness of breath, abdominal pressure, frequent vomiting, a high fever, if you have underlying conditions, or are at risk of developing complications from flu.

Cold or allergies quiz: 4 questions to help identify the illness


Question: Do your symptoms last a month or more?

Yes: Sounds like allergies. If your sneezes and sniffles persist beyond allergy season (which varies by location, but roughly lasts from spring through summer and into early fall), see an allergist to rule out chronic allergies (such as reactions to dust mites and/or mold).

No: Could be a cold. Take it easy and see a doctor if you start producing colorful mucus (anything other than clear) or if symptoms worsen or persist longer than two weeks.


Question: Do the symptoms return every season?

Yes: Sounds like allergies. For most seasonal allergies, Dr. Emanuel says the triggers are usually obvious—for instance, if you go running in the grass and your eyes start watering, consider a grass allergy. Or if pollen counts are high and you’re suddenly sneezing, a pollen problem is likely. You can try an over-the-counter allergy medication, but the best practice is to avoid the trigger in the first place. See an allergist if you have questions or if symptoms persist.

No: Could be a cold. Take it easy, and see a doctor if symptoms worsen or persist beyond two weeks.


Question: Do you have itchy, watery eyes?

Yes: Sounds like allergies—colds almost never produce this symptom, says Dr. Emanuel.

No: Could be a cold. Take it easy, and see a doctor if symptoms worsen or persist beyond two weeks.


Question: Are you experiencing your symptoms in winter?

Yes: Sounds like a cold.

No: Could be a cold or allergies. Check the chart above to narrow down your other symptoms, and see your doctor if you’re really uncomfortable and not getting better after a few weeks.

How to prevent colds, flu and allergies

Frequent hand washing and avoiding others who are contagious are the best ways to prevent cold and flu. Allergies are a bit trickier, but in general, staying away from the triggers that cause them is the best solution. 

At the end of the day, colds, flu and allergies are common, if unpleasant, parts of the human experience. Do your best to avoid them, and when that doesn’t work (and sometimes it just won’t, no matter how hard you try), take it easy on yourself. 

Learn more about treating allergies in our guide to natural antihistamines. Dealing with a cold or flu? Rest as much as you can, avoid spreading your germs to others and call your doctor if you’re concerned, if your symptoms last more than two weeks, or if the misery is too much to bear.

References +
  1. HealthLinkBC. Difference Between Influenza (Flu) and a Cold. https://www.healthlinkbc.ca/health-topics/abr7766
  2. Centers for Disease Control and Prevention. Cold Versus Flu. https://www.cdc.gov/flu/symptoms/coldflu.htm
  3. Claritin. Is it Allergies or a Cold? https://www.claritin.com/living-with-allergies/allergies-or-a-cold
  4. HealthLinkBC. Difference Between Influenza (Flu) and a Cold. https://www.healthlinkbc.ca/health-topics/abr7766
  5. NIH News in Health. Cold, Flu, or Allergy? https://newsinhealth.nih.gov/2014/10/cold-flu-or-allergy
  6. Victoria State Government Better Health Channel. Flu (influenza). https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/flu-influenza
  7. UPMC HealthBeat. Why Do I Have the Chills? https://share.upmc.com/2016/08/why-do-i-have-the-chills/
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