Why Flu Versus a Cold Matters, Explained Simply
Flu Versus a Cold: what it is, why it matters, and what published guidance actually asks of you.
Flu can lead to pneumonia and hospitalization, and antiviral medicines for flu work best when started early, so knowing the difference affects when to call a doctor.
Key takeaways
- Flu onset: sudden: fever, chills, body aches, headache and exhaustion
- Cold onset: gradual: runny or stuffy nose, sneezing and sore throat
- Most useful single change: Get a flu vaccine every fall.
- Commonest mistake: Antibiotics for a cold or flu; they do not treat viruses.
- See a doctor if any of the signs under "When to speak to a doctor" below apply to you.
The short answer
How to tell influenza, a potentially serious viral illness, from a common cold caused by other respiratory viruses.
Where it fits
This is part of Infectious Diseases. Guidance sets out what to look for and what to do about it, which is what the rest of this page covers.
The numbers, in one place
| Measure | Figure |
|---|---|
| Flu onset | sudden: fever, chills, body aches, headache and exhaustion |
| Cold onset | gradual: runny or stuffy nose, sneezing and sore throat |
| Flu antiviral medicine | works best started within 48 hours of symptoms |
| Yearly flu vaccine | everyone 6 months and older, ideally by the end of October |
| Back to normal activities | when symptoms are improving and you have had no fever for 24 hours without medicine |
What that means in practice
The practical version:
- Get a flu vaccine every fall
- Call your doctor early in a flu-like illness if you are 65 or older, pregnant, or have asthma, diabetes, heart disease or another chronic condition
- Rest, drink plenty of fluids and use acetaminophen (Tylenol) or ibuprofen as the label directs
- Wash your hands often and cover coughs and sneezes
What gets people into trouble
Common wrong turns:
- Antibiotics for a cold or flu; they do not treat viruses
- Giving aspirin to children or teens with flu-like symptoms, because of the risk of Reye's syndrome
- Cough and cold medicines in children under 4 without a doctor's advice
Related topics
- Colds and Flu: What Published Guidance Supports (Immunity)
- The Evidence on Pneumonia, Without the Hype (Respiratory Health)
- The Evidence on Vaccination in Older Adults, Without the Hype (Healthy Aging)
- Common Childhood Infections: What the Evidence Actually Says (Children's Health)
Where to go next
- Answers to the Common Questions on Flu Versus a Cold
- Flu Versus a Cold: Just the Figures
- Flu Versus a Cold — the reference entry
- Infectious Diseases: The Complete Guide
- Measles: What the Evidence Actually Says
- Lyme Disease and Ticks: What Published Guidance Supports
When to speak to a doctor
Call your doctor if symptoms improve then return with fever and a worse cough, or if a cold lasts more than 10 days. Call 911 for difficulty breathing, chest or belly pain or pressure, new confusion, seizures, severe dehydration, or in a child, fast breathing, bluish lips or face, or ribs pulling in with each breath.
Where this comes from
How this page was put together
Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarized or generalized beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to your doctor, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 911.
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