Can cold and flu nasal sprays stop you getting sick when flying?

Products such as Nasaleze Travel (£8.95, Boots) and Biosure Pro Protective Nasal Spray (£9.95, Well) are marketed specifically at travellers packed into planes and trains. 

Nasaleze Travel is claimed to ‘shield and protect from airborne germs and viruses’. Biosure states that it blocks and inactivates ‘99% of colds, flu, rotaviruses and coronaviruses’. And both products are claimed to be ‘clinically proven’. But can they really stop us picking up a cold, flu or covid when we fly?

We asked Professor Ronald Eccles (founder of the Common Cold Centre at Cardiff University), Dr Matthew Siggins (National Heart and Lung Institute) and community pharmacist Michael Line to look at the evidence from the manufacturers. 

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Why do I always get a cold on the plane?

It seems to happen so often that many of us worry planes are full of air that recirculates viruses. 

In fact, that’s not the case. HEPA (high-efficiency particulate air) filters in modern planes keep air cleaner than in most indoor environments. 

But low humidity on a plane is a problem. It dries out nasal passages and makes us more susceptible to infection if somebody nearby is ill. 

And of course, any situation where we're in close proximity to many other people makes the transmission of a cold - a highly contagious virus – and other respiratory diseases much more likely. It can spread through direct touch, a sneeze, a cough or contaminated objects. 

How does Nasaleze Travel claim to work?

The manufacturers say Nasaleze creates a ‘physical barrier’ in the nose that traps and deactivates airborne germs and viruses, which are then swallowed and destroyed by stomach acid. The key ingredient is hydroxypropyl methylcellulose (HPMC), which is used as a gelling agent in sauces by the food industry.

The problem with this theory, says Professor Eccles, is that ‘the nose already has a barrier – mucus – which is an extremely potent means of trapping viruses’. HPMC may support that barrier, he says, but adds: ‘I’m not convinced it would prevent a cold.’

Dr Siggins also has doubts, pointing out that mucus is cleared from the nasal tract and swallowed roughly every 20 minutes, so it’s likely the barrier would disappear with it. ‘Nasaleze may remain in the nasal tract longer,’ he says, ‘but this hasn’t been shown.’

Nasaleze told us that mucociliary clearance is ‘slowed significantly when a cold develops’ and that Nasaleze’s dose is ‘three times a day, or every time a patient sneezes’. It pointed to evidence of 55 studies, nine of which were specifically for the travel product. Of these, five were in vivo (human) trials. ‘We are unaware of any other medical devices with as many studies,’ it said.

Does Nasaleze Travel work?

‘It may work, but the evidence is weak,’ said Prof Eccles, pointing to an overreliance on laboratory evidence, and human trials using small numbers of participants. 

Dr Siggins agrees: where the manufacturers did provide evidence of studies in humans, in his opinion, they ‘are not particularly robust, lack transparency and have a high risk of bias’. 

How does Biosure Pro Protective Nasal Spray claim to work?

BioSure Pro is also claimed to form a physical barrier. According to the manufacturer, this barrier protects against infection by respiratory viruses for up to six hours. 

It's also said to contain a ‘magical’ positively charged ingredient – ethyl lauroyl arginate hydrochloride (ELAH) – that attracts negatively charged viruses, before attacking them. ‘Imagine ELAH like a child with a safety pin in a room full of balloons,’ its website proclaims.

Our pharmacist Michael Line was not convinced. ELAH belongs to a family of chemicals known as cationic surfactants – commonly used as soap. ‘We already know that soap is effective in destroying bacteria and viruses,’ he says, but ‘whether squirting it up the nose is equally effective has yet to be determined.’ 

Does Biosure Pro work?

Professor Eccles felt that the evidence of antiviral activity from lab experiments provided by BioSure Pro was ‘interesting’. ‘It may provide some benefit,’ he says ‘but the evidence is still weak when it comes to human clinical trials.’ 

BioSure told us that its ‘clinically proven’ claims relate to 25 studies that evidence the safety and efficacy of creating a temporary barrier in the nose. It also said it’s investing a seven-figure sum in a large human clinical trial in the UK, which is underway, and it plans to publish preliminary results in 2024.

‘It’s a plausible mechanism,' says Dr Siggins, ‘but there’s a lack of supporting evidence.’

Nasaleze Travel and Biosure Pro are not medicine

Professor Eccles told us that ‘the over-the-counter cold and flu market is dominated by stories and claims, not science’. There is clever marketing at play, too. Nasal sprays are registered as ‘medical devices’, not a ‘medicine’. 

Manufacturers are required to jump through fewer hoops to get a medical device licensed, explains pharmacist Michael Line, but that ‘does not involve detailed examination of medical claims’. 

He also says there’s no official definition of ‘clinically proven’ for medical devices: ‘It can be used quite freely.’

Both Nasaleze and Biosure told us that they’re registered as medical devices because the ingredients are inert, with no pharmacological activity. 

Biosure said that ‘the formula does not contain any ingredients of a medicinal nature’. It also told us that the generic definition of ‘clinically proven’ is that ‘the product has been tested during clinical trials or studies’.

What about other nasal sprays such as Vicks First Defence, Boots Dual Defence and Lemsip First Action?

There are several other nasal sprays with claimed antiviral properties that dominate the market. 

Products such as Boots Dual Defence (£4.37, Boots) and Lemsip First Action (£7.35, Boots) use carrageenan – a seaweed extract that some clinical trials have shown can reduce the symptoms and duration (by two days) of the common cold. 

And Vicks First Defence (£7.85, Boots) creates an acid environment at the back of the nose, which Vicks claims attacks and damages viruses. 

But none of these products are marketed as preventative. In fact, both Boots (in 2015) and Vicks (in 2020) were rapped by the Advertising Standards Authority for implying their nasal sprays could be used to prevent a cold. Instead, these sprays are to be used when the first symptoms appear.

Would our experts use travel nasal sprays to prevent a cold?

Two of our experts said ‘no’, citing weak evidence that they prevent infection – although they’d reassess if stronger evidence emerged. Instead, both recommend washing hands and wearing a mask as more effective. 

Professor Eccles, however, said he always uses the carrageenan nasal sprays, such as Boots Dual Defence and Lemsip First Action, because of the clinical evidence behind its antiviral properties. ‘For me,’ he says, ‘if it works to reduce the symptoms when you’ve got a cold, it could be useful in preventing colds.'

How can I prevent illness when flying?

• Be careful who you fly with Some airlines do a better job than others of cleaning their plane. 
• Wash your hands This is your best defence against grubby surfaces. And if you do touch seat backs on your way back from the toilet, sanitise your hands again before eating.
• Wipe the tray table Wipe this down before placing food on it.
• Use the overhead ventilator Do switch this on as it will disperse any microbes coming from your neighbours.
• Chuck it away Forget the so-called ‘five-second rule’. If you drop a biscuit on the floor in an aeroplane, throw it away.