With winter well and truly upon us, so is the yearly wave of colds and flu, making now the perfect time to think about protecting yourself and others.
You know the drill: wash your hands often, cover your coughs and sneezes, avoid touching your face, keep indoor spaces ventilated, stay home if you feel unwell and get a flu shot.
But beyond this familiar advice, there are also useful steps you can take that you might not know about. Here are the latest findings and lesser-known strategies to help get you and your family through the cold and flu season.
Humidity is key
It’s common knowledge that ventilation is important to help stop the spread of cold and flu viruses. But what’s often overlooked and plays an equally important role in how these viruses spread is humidity.
Research shows that flu viruses survive longer in dry air, which is why outbreaks often peak in winter when central heating dries out our homes and workplaces.
Low humidity also makes the tiny droplets we exhale evaporate into even smaller particles. These can float in the air for longer and travel further, giving the virus more chances to spread.
Dry air also weakens the body’s natural defences by drying out the protective mucus in our eyes, nose and throat.
This makes it harder to trap and clear away germs, which not only increases the risk of infection, but also slows recovery time and makes symptoms like coughs, sore throats and congestion worse.
Evidence suggests that maintaining indoor humidity in the ‘Goldilocks zone’ of 40–60 per cent makes the environment less hospitable to viruses, while helping our airways stay moist and better able to fight off infections.
Although it’s important to keep crowded spaces ventilated, in winter it often brings in cold, dry air that actually lowers indoor humidity. That’s why scientists recommend balancing fresh air with the right level of humidity to help reduce the spread of colds and flu.
The most effective way to add moisture to the air is with a humidifier, especially those with built-in controls that regulate humidity levels.
The exercise myth
For decades, the conventional thinking was that endurance sports temporarily suppress your immune system, increasing the chances of illness.
But in 2018, Dr John Campbell, senior lecturer in the department of health at the University of Bath, turned this idea on its head. His research showed that exercise could actually boost the body’s immunity.
“When we do strenuous exercise, the number of immune cells circulating in the blood temporarily increases. After exercise, levels drop below baseline, which was once thought to be an ‘open window’ for infection,” says Campbell.
“We now know that these immune cells aren’t lost. Instead, they move into tissues that are more likely to become infected, such as the lungs, to hunt for infections. This suggests that exercise can actually enhance the immune system.”
Campbell stresses that exercise is good for health and helps protect against disease, so people shouldn’t fear that it weakens immunity.
He says, “Aerobic exercise, such as running or brisk walking, is great for boosting the circulation of immune cells.
"We also now know that resistance training (lifting weights) plays a role too, as muscle tissue releases proteins that support immune function. Combining both types should give the best, broadest support to your immune system.”
Read more:
- Will we ever find a cure for the flu?
- Having a cold blocks you from catching the flu
- How are seasonal flu vaccines made?
Prioritise vitamin D over vitamin C
While vitamin C may help to slightly shorten the duration of an illness, there’s unfortunately little evidence that it can prevent us from getting ill in the first place. Vitamin D, on the other hand, has been proven to help strengthen our immune systems.
18 per cent of adults aged 19–64 in the UK are deficient in vitamin D. The NHS recommends that everyone take a daily supplement of 10 micrograms of vitamin D during the darker months (October to March).
There are two types of vitamin D supplements available: vitamin D2 and vitamin D3. A recent study, however, found that taking vitamin D2 may actually lower our levels of vitamin D3 – the kind our bodies use to support the immune system.
“We found that people given vitamin D2 had a drop in vitamin D3 levels, even compared with those who took no supplements at all,” says Emily Brown, lead researcher of the study at the University of Surrey.
Prof Susan Lanham-New, co-author of the study, adds: “Vitamin D2 seems to activate an enzyme in the body that speeds up the breakdown of vitamin D3. Studies also show that D3 switches on helpful genes that strengthen antiviral and antibacterial defences, while D2 doesn’t appear to have this same effect.”
Brown stresses that everyone in the UK should still take a vitamin D supplement: “Our study suggests that vitamin D3 is the best option, but further research is needed to fully understand the long-term differences.”
Flu jabs aren't just for grandparents
Another common myth is that only older people or those with serious health conditions need the flu jab. In reality, flu can affect anyone. Even healthy adults can become seriously ill.
Being essentially little germ factories, children are the biggest spreaders of flu. It can also make them very unwell because their immune systems are still developing, and their smaller airways make them more prone to serious complications such as bronchitis and pneumonia.
In fact, children under five have some of the highest rates of flu-related hospital admissions.
It’s for these reasons that the UK government recommends the flu vaccine for all children aged two and above, up to the age of 16.
In 2025, it expanded the vaccination programme so that two- and three-year-olds can also get their jab at community pharmacies, making it easier for families to protect their little ones, as well as everyone around them.
Many people also don’t realise that, as an adult, you can still get a flu jab privately, even if you’re not eligible for a free NHS one.
Pharmacies and some GP practices offer it for a small fee, usually at a price point of around £15–£25, so you can cheaply and efficiently protect yourself if you’re worried about catching flu.
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