How sucking on a zinc lozenge really CAN cut three days off a cold: As Covid, flu and winter bugs surge, experts reveal the exact dose that actually works… and why ordinary supplements are a waste of money

Covid, flu and common colds are on the rise across Britain, with health chiefs warning of ominous signs of an unusually difficult winter ahead.

The latest surveillance figures show Covid infections climbing, while flu-like illness and other respiratory infections are also increasing – in some cases above levels normally expected at this time of year.

Meanwhile, the NHS has reported its busiest September on record, with 2.44 million A&E attendances and more than 800,000 ambulance incidents.

So, with millions of us facing the prospect of coughs, sore throats and streaming noses in the coming months, is there anything we can take to stop a cold in its tracks – or at least shorten the misery?

Pharmacy shelves are packed with remedies promising quick relief. But while experts say there is no magic cure, some evidence suggests certain treatments really can help shorten the duration of a cold.

Among the most promising is zinc, a popular supplement thought to support the body’s immune response to the viruses responsible for the common cold.

Available over the counter in everything from capsules and lozenges to nasal sprays and drops, it has long been touted as a way to ease symptoms and speed recovery.

However, experts warn that not all zinc remedies work in the same way – and choosing the right formulation could make all the difference.

Does the form you take your zinc in matter?

It sounds almost too good to be true. But some research suggests that sucking on zinc lozenges could cut several days off the misery of a common cold.

A 2016 analysis of three clinical trials involving 199 people found that those given zinc acetate lozenges recovered almost three days sooner, on average, than those taking a placebo. Without the treatment, colds lasted around a week.

And a larger review of the evidence, published by the respected Cochrane Collaboration in 2024, concluded that zinc could shorten a cold by around two days – although researchers cautioned that the quality of the evidence was limited.

However, Dr Harri Hemilä, a researcher at the University of Helsinki in Finland who has spent years investigating zinc and the common cold, says there is an important catch: ordinary zinc tablets do not appear to offer the same benefit.

‘There is very strong evidence that zinc lozenges can shorten the duration of colds,’ he says.

‘However, there is no meaningful evidence that ordinary tablets, which are swallowed whole, would have an effect on cold duration.’

Unlike tablets, which are swallowed immediately, lozenges dissolve slowly in the mouth, releasing zinc into the saliva and exposing the mouth and throat to it for longer.

One theory is that this allows zinc to interfere with the ability of cold viruses to infect cells and multiply, although precisely how it works remains uncertain.

And even among lozenges, the formulation appears to matter.

How much you need – and when you should take it

Even if you choose a lozenge rather than a tablet, there’s another catch: many products sold in pharmacies may not contain enough zinc to make a difference.

Dr Hemilä argues that some commercial lozenges are unlikely to work because they contain too little zinc, or include ingredients such as citric acid that may interfere with its action.

He says studies suggest that around 100mg of zinc a day – usually spread across several lozenges – may be needed to achieve the best results.

But this is considerably higher than the 25mg daily upper limit recommended by the NHS for zinc supplements, unless advised otherwise by a doctor.

Taking too much zinc can cause nausea and stomach problems, while prolonged high intake can interfere with the body’s absorption of copper, potentially leading to anaemia and neurological problems.

However Dr Hemilä’s recommendation is for a short-term therapeutic dose, rather than a recommendation for routine daily zinc supplementation.

And there is another factor to consider: timing.

‘Studies show the greatest benefit was when people started zinc within 24 hours of cold symptoms,’ says Dr Hemilä.

‘As a general rule, I would say that with cold symptoms, the sooner the better.’

So why aren’t all doctors recommending zinc?

Despite these apparently promising findings, not all doctors are convinced that zinc is worth taking.

Dr Dean Eggitt, an NHS GP, says the evidence is not strong enough for him to recommend it routinely.

‘There is some evidence that it might reduce the number of days that you have an infection, but the research isn’t good enough to categorically say yes, it will work,’ he says.

Professor Daniel Davis, professor of immunology and head of life sciences at Imperial College London, explains that the studies aren’t always as straightforward as headlines might suggest.

‘The overall message from the research on zinc is a bit mixed. Some studies say it can help, and others say it definitely doesn’t. All of these things are complicated,’ says Professor Davis, author of Immune Health: A Myth-Busting Guide.

He also points out that most people already get enough zinc through their normal diet, from foods including meat, cheese, bread and cereals.

And while taking a lozenge at the first sign of a cold may offer some benefit, he says looking after your immune system more generally is important too.

‘Your immune cells clearly work less well when stress hormones are high, so trying to avoid stress and getting good sleep, where possible, can help your body fight off infections,’ he says.

‘Regular exercise is also important for keeping the immune system strong, although you shouldn’t be doing strenuous exercise in the middle of a cold.’

What about Vicks First Defence’ spray?

But what about zinc nasal sprays? One of the best-known cold remedies on the high street is Vicks First Defence, which contains zinc and claims to help stop a cold developing when used at the first sign of symptoms.

However, research suggests a much simpler remedy could work just as well.

In a major clinical trial led by researchers at the universities of Southampton and Bristol, scientists compared Vicks First Defence with a simple saline nasal spray – essentially salt dissolved in water – and usual care.

They found that both sprays shortened the duration of respiratory illness by around 20 per cent compared with usual care.

People receiving usual care were ill for an average of 8.2 days, compared with 6.5 days among those using First Defence.

Crucially, however, the saline spray was just as effective.

Professor Paul Little, from the University of Southampton, who led the trial, explains: ‘The key thing was that people were asked to use the sprays at the very first sign of illness.

‘Saline had an identical effect to the Vicks spray in terms of benefits but fewer side effects as Vicks had a small increase in the number of people reporting headache.’

The findings suggest that while First Defence contains zinc, it may not be the zinc itself that is responsible for any benefit. The spray’s other ingredients are designed to help trap and inactivate viruses, while saline may help by washing virus particles out of the nose.

‘Since saline worked as well as Vicks and had lower side effects, it is the clear winner,’ Professor Little says, adding that he would recommend using a saline nasal spray at the first sign of a cold.

Dr Eggitt puts it simply: ‘Your immune system clears the cold – medicines just help you feel human while it does the work.

‘There’s no magic cure that stops a cold in its tracks – only things that help you ride it out.

‘The boring stuff your parents told you – rest, fluids, warmth – still matters more than fancy cold cures.’