Hey there, time traveller!
This article was published 7/3/2015 (1683 days ago), so information in it may no longer be current.
It's still sniffle season. All you can do for your cold is treat its symptoms. Or so say lots of websites. Physics says they are wrong: You can treat your cold infection using heat.
Any one of some 400 kinds of viruses can cause a cold. Like all human viruses, they bear protein molecules on their surface. They use these protein molecules to hijack the machinery of human cells and make more virus particles. Quantum theory explains how physical bonds, called hydrogen bonds, hold each protein molecule in a unique shape that, as a key fits a lock, enables the molecule to do its dirty work. Heat causes molecules to move about — first explained by Albert Einstein in his doctoral thesis. This can tear hydrogen bonds apart and bend protein molecules out of their key shapes. At 65 C you can scramble eggs, or scald your mouth, by breaking bonds in proteins. A lower temperature — that does not hurt you — can break enough hydrogen bonds to temporarily prevent a cold virus from invading cells or, if they are inside already, from breaking out to infect more cells.
How can you use these principles to stop your cold? It takes only five minutes, but you should do this within hours after that pre-cold sore throat begins: Add a pinch of salt to half a cup of hot water and stir till it dissolves. The salt solution should be almost — but not quite! — too hot to hold your thumb in for a few seconds. Microwave it or add water to get this right. Gargle with a mouthful to confirm the temperature; it should feel like a hot drink but not scalding. Then, and this is the key step: Lift the cup up to your nose, snort the rest back through the nasal cavity and spit it out. OK, it doesn't feel good and it is disgusting. But it's less bad on both counts — and much briefer — than the cold you have just stopped in its tracks. You can repeat the process if the pre-cold throat returns.
Why does it work? A cold infection starts in the cells that line your nasal cavity. At an early stage of infection, the virus particles are still near the surface. To continue the infection they must do three things: Unlock a way into your cells; use your cells' machinery to multiply and unlock a way out to infect more cells. It's the temperature of the salt solution that stops the infection from progressing. The salt just makes the water user-friendly for your tender tissues. The temperature, about 45 C, and brief exposure won't hurt your cells. Nor are they hot enough or maintained long enough to kill the virus. But the heat will discombobulate the viral proteins. They lose their special shapes. So, at least for a while, they can't perform their key-and-lock routines. This gives your immune system time to kill the virus particles before their rapid replication runs amok.
Try it. You need never suffer through a cold again. At the same time you'll boost your own immunity to reinfection by the same cold bug. And stopping colds and preventing sick days with simple physics could boost the North American economy by some $30 billion per year once word gets around, so tell your friends.
Colin Gillespie is a physicist and author whose most recent book is Time One: Discover How the Universe Began. He writes a weekly web blog Science Seen.