It contains a polymer (HPMC) based on cellulose extracted from North American conifers grown in renewable forests, Pyroglutamic acid that occurs naturally in fruits and vegetables such as tomatoes and natural eucalyptol and menthol.

The spray literally traps cold germs, makes them harmless and then helps your body get rid of them naturally – so you might have a runny nose for a few minutes after taking it. This helps stop a cold before it really gets hold.

Colds start in the nasopharynx, that’s the bit that connects the back of the nose to the back of the mouth. The micro-gel nasal spray works in this area and helps stop a cold in it tracks.

Because it hasn’t been clinically tested against Influenza, the truthful answer is that we don’t know.

The way it works doesn’t depend on the specific cold virus. Without getting too technical, what the gel does is make your nasopharynx a very unfriendly place for cold viruses by lowering the pH. All cold viruses are sensitive to pH, that’s why the spray works against all of them.

It works best if it's taken when you think you might be at risk of getting cold, like if you're around lots of sniffly people. Or when you start getting the first signs of a cold, before it has chance to develop. It doesn't work when you've already got a full-blown cold.

Because the spray doesn’t work specifically against viruses, but on changing the environment they live in, it’s highly unlikely that cold viruses could become resistant to it.

You should continue taking it for a couple of day after all the signs that you might be getting a cold have disappeared. This is to make sure that the virus has totally gone. If you stop using the spray too soon, there may still be viruses in the environment, in your nose or on their skin that might start a new infection.

Because it’s only designed to be used for a few days, it’s highly unlikely that the good bacteria in your nose – the microflora – would be affected by the spray.