The common cold can be cured with salt water because the body uses it to produce anti-viral bleach, scientists say.
Nose drops and gargling salt water were shown to reduce the average length of the virus by up to two days in a study.
Participants who used the method were less likely to need over-the-counter medications and less likely to pass their cold on to family members, compared to those who did not.
Cells in the body use the chloride in salt to produce hypochlorous acid (HOCI) which is the active ingredient found in bleach.
The researchers, at the University of Edinburgh, have been aiming to find a low-cost option to treat the incurable common cold.
They are now looking at whether the home remedy can be used as a viable method to treat the virus in children.
The Edinburgh and Lothians Viral Intervention Study (ELVIS) involved 54 participants who confirmed they had symptoms of a cold.
Researchers asked 30 people with colds to add three grams of Cornish sea salt to a 100 millilitre bowl of boiling water.
After waiting for it to cool, they blocked one nostril and inhaled the water through the other, repeating this for both nostrils three times each. Study participants then gargled three times with the remaining salt water.
These people were compared to 31 people who did nothing to treat their cold, with both answering daily questions on their symptoms until two days after they got better.
For those using the salt solution, their cold ended 1.9 days earlier, with their blocked nose clearing 2.7 days sooner than those who let the cold run its course. Sneezing came to an end 1.5 days earlier, with coughing easing 2.4 days faster.
Among the 57 people who filled out questionnaires after their illness ended, 35 per cent fewer people using the salt solution said someone else in their home had caught their cold and suffered similar symptoms.
The cold virus is passed on in the air through speaking and breathing, and the likelihood of this happening can be measured based on someone’s ‘viral load’.
To do this, researchers examined five days of early-morning nasal swabs from the people in the study.
The results show people who used salt water appeared to be less contagious. They were 30 per cent more likely to see a significant reduction in the amount of virus in their body.
Dr Sandeep Ramalingam, the virologist who led the research, said: ‘It is an extremely simple measure to take for someone who is battling a cold.’
The average adult gets a cold three times a year, which is unpleasant enough in itself but can also lead to respiratory problems like pneumonia.
There is no cure because so many different viruses cause the common cold, which leaves sufferers desperate for ways to cut their illness short and relieve the symptoms.