Question
What causes the common cold?

Answer
What is a cold? When someone says, "I have a cold" what they mean is, "there is something in my body that is causing me to have the set of symptoms that we call 'a cold'". The set of symptoms normally includes things like a runny nose, sneezing, coughing, "chills" and a headache. It does not include a fever - normally if there is a fever that would be called "the flu".

There are many different viruses that can cause cold symptoms, but about half of the time a cold is caused by a class of viruses called rhinoviruses. The virus gets into the cells lining your nose and starts reproducing. It arrives from other people - it is not cold weather that causes a cold, but the fact that cold weather causes people to congregate together indoors that makes transmission of the virus easier. The virus generally moves from someone else's hands to your hands (either directly or through some intermediate surface like a door knob), and from your hands into your nose or eyes.

Your body reacts to the presence of the virus with its immune system. The HSW article entitled How the Immune System Works talks about infectious diseases and how your immune system deals with them. In the case of a cold, the immune system opens up blood vessles through inflammation and also increases mucus secretions. These two processes give you the runny nose and the stuffy feeling. The irritation caused by the virus and all the fluid causes sneezing. If the virus makes it into the cells lining the lungs, then they start producing fluid and mucus too and that produces the cough. As the immune system gears up over several days and fights the virus, the mucus will thicken and change color with dead cells (a form of pus, really). Eventually the immune system eliminates the virus completely and you are well again!

Here are several interesting and helpful links:

• The Truth about Viruses
• The common cold
• The Rambling Rhinovirus - light introduction
• Uncommon common cold
• Science Behind the Cure for Common Cold - scientific studies around zinc lozenges
• Zinc - A weapon against the common cold? - from the Mayo clinic
• Zinc for the Common Cold? - a more skeptical look at zinc lozenges
• Vitamin C for the common cold - scientific study
• Rhinoviruses - deep technical information

How Stuff Works Power Panel

Table of Contents A complete list of all HSW articles About Marshall Brain Information about the creator of HSW Search Search for any word or concept in HSW Citing HSW Information about citing HSW in articles and papers Question of the Day Ask questions or browse hundreds in the archive Books A variety of books for people interested in how stuff works HSW Newsletter Sign up to receive the monthly HSW newsletter Contacting HSW Contact HSW directly with email What's New Review newsletters to chart HSW's development Awards Check out HSW's awards and reviews! Disclaimer The disclaimer required by the lawyer Author Information Learn how you can write for HSW HSW Fan Buttons Link to HSW with these snazzy fan buttons! Suggestions Leave a suggestion in the suggestion box

How Stuff Works (http://www.howstuffworks.com) is a production of BYG Publishing, Inc. http://www.bygpub.com - questions@bygpub.com P.O. Box 40492 - Raleigh, NC 27629

© 1998 BYG Publishing, Inc. All rights reserved.