[Justin Kobow]

Justin Kobow  asked the Naked Scientists:
   
When I was a kid and I had a sore throat my mum would have us gargle salt water. I could never tell if it helped but I was wondering does gargling salt water help a sore throat and if so how?

Thank you
Justin from Des Moines, Iowa

What do you think?

[Chemistry4me]

I think perhaps it helps removes mucus from the throat, which makes it feel better.

[Raghavendra]

and cool

[chris]

Let's look at this step by step.

Sore throats are usually caused by viruses (80% of the time) and therefore the soothing effect of the salt cannot be down to microbial growth suppression. Also, the effect occurs too quickly for that to happen.

When the throat is sore owing to infection the soreness is caused by the release of inflammatory mediators (chemicals) produced when the mucosal surface is injured by microbial action (viruses replicating and sloughing off the cells). The pain occurs partly because the inflammatory mediators lower the threshold (increase the sensitivity) of the nociceptive (pain) nerve fibres that detect tissue injury.

Therefore the relief provoked by gargling with salt could be down to several factors:

1) It washes away some of the inflammatory mediators.
2) It desensitises the pain fibres temporarily so they stop firing and hence the sensation of pain is reduced.
3) It washes away other chemicals that are activating the nerve fibres and hence reduces discomfort.

In relation to 3) I think that salt is quite good at disaggregating mucus (which is chiefly the protein mucin), and this might have pain-relieving properties if the mucus is trapping a layer of inflammatory chemicals against the mucosal surface.

Chris

[DrN]

Could the salt have anything to do with osmotic potential of cells? clutching at straws somewhat, but thought I'd throw it out there!

And isn't salt used to preserve things? therefore it must have antibacterial properties, so maybe it prevents or treats secondary infections? So, no direct action on viral infections, but would act to ease say, strep throat?

[chris]

I discounted the bacterial growth-suppression angle on the grounds that the relief is almost instantaneous, which doesn't really fit with altering bacterial growth dynamics.

Chris

[Steppenwulf]

That salt gargling washes away inflammatory chemicals makes sense. But that doesn't really need salt does it - gargling with plain water would do. I'm not sure if salt also has an effect on pain sensing neurons.

But another mode of action could be to do with a negative action on throat bacteria, no? Even when the primary cause of the disease is viral, the thick mucosa can provide a nice environment for some bacteria. Progression of a viral infection to a bacterial one, such as a cold to strep throat is not unusual.

Perhaps in addition to washing away inflammatory chemicals, the salt may change the micro-environment making it saltier andt less hospitable to most bacteria (osmotic pressure and all that). It may also affect the structures bacteria build to stay in place (usually built of poly saccharides and peptides, if I remember from my school days), helping to wash away more of the bacteria, if you gargle more than once.

So a primary effect of washing away bad things, and a secondary effect of making it harder for bad bacteria to live in the throat sounds like a reasonable mechanism for action.

As this is just random speculation, any comments on whether this makes sense are appreciated...

[SteveFish]

I prefer a tequila gargle and I swallow to make sure it actually reaches the throat area. I find with a nasty cold that I feel much better after some ibuprofen and a few gargles.

[RD]

Isn’t gargling similar to "rubbing it better"  … http://en.wikipedia.org/wiki/Pain#Gate_Control