UK mosquitoes: Everything you need to know

Telegraph

29-04-2025

Humans have been locked in a war with mosquitoes for thousands of years. The Ancient Greek historian Herodotus wrote of workmen on the Egyptian pyramids who were given garlic as a deterrent, while in 835 the festival of Hallowmas (All Saints' Day) was moved from May to November by the Pope, because of the sheer number of pilgrims dying of malaria on their trek to Rome.
We are lucky enough not to have any mosquito-borne diseases circulating in the UK, but in recent summers there have been reports of swarms of them in parts of the country – and if temperatures follow a similar pattern we could suffer through another bite-filled summer.
It seems as if our ways of repelling them haven't progressed that much since the days of Herodotus. Research from Johns Hopkins University suggests that eating herbs or spices like sage and cardamom could be the key to keeping your blood supply to yourself.
Here, we look at whether a nightly curry really can repel the little blighters – and everything else you need to know about mosquitoes.
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Are there mosquitos in the UK?
What do British mosquitos look like?
Is Britain's mosquito problem getting worse?
Do some people really get bitten more than others?
Can what you eat ward them off?
Mosquitoes vs midges
How to control mosquitoes
What are the best treatments for mosquito bites?
Are there mosquitoes in the UK?
There are 36 species of mosquitoes which are native to Britain and more than 3,500 species worldwide. Of the 36 native to Britain, Culiseta annulata is one of most common and the most unwelcome: it has a wingspan of nearly an inch and a painful bite that leaves a red itchy lump. Unfortunately, they are particularly partial to people.
Hope instead that the whining in your ear comes from the Culex pipiens, another common species which often invades British homes, but which prefer feeding on birds. That said, a sub-type of the Culex pipiens is found in cities – particularly on the London Underground – and has evolved to have rather a penchant for you and me.
What do British mosquitoes look like?
The Culiseta annulata variety has a wingspan of 13 to 15 mm and they are one of the largest mosquitoes. Their wings are spotted. Members of this family have a long forward pointing proboscis and the males have feathery antennae.
Culex pipiens are medium-sized mosquitoes and tend to be 4 to 10mm. They are brown and don't have any obvious distinguishing patterns.
Is Britain's mosquito problem getting worse?
The amount of mosquitos changes every year due to the weather: long, hot summers punctuated by periods of rain, when they can breed, will produce far more than cooler and dryer spells. Kent is one of the worst affected parts of Britain – in recent summers, areas around the River Stour have become inundated – because it is warm with plenty of marshland.
'Overall, I don't think there are more mosquitoes, but there are new species,' says Prof James Logan, a principal investigator at the London School of Hygiene & Tropical Medicine.
He cites the recent arrival of the Aedes mosquito – a particularly dangerous species that originated in Africa and which bites 24 hours a day, rather than just at night.
It can transmit dengue and yellow fever and has been the cause of hundreds of thousands of deaths in other parts of the world. In the UK, Aedes tend to congregate in areas near motorways as they are usually brought over on lorries; thankfully, they can't yet survive a British winter so mass dengue and yellow fever transmission remains unlikely (while still being possible) until the climate gets significantly warmer.
Do some people really get bitten more than others?
Yes. The hotter and sweatier you are, the more likely you are to get bitten. But mostly, it's about luck: certain people produce higher levels of carboxylic acids and other natural repellents on their skins and so will always bat away more mozzies.
'There is still more research to be done on where this natural repellent comes from – but it could have a genetic component, or it could be down to our individual microbiome,' says Logan.
Less fortunate are those who react strongly to the anticoagulants mosquitoes inject to ensure they get a decent amount of blood, meaning their bites will be bigger, itchier and more noticeable – although this changes over the course of your life.
'The first time you are bitten you don't react,' says Logan. 'The next time there is a bit of a reaction, and so on, until you become sensitive and every site gets swollen and very itchy.' Conversely, if you get bitten enough, the body eventually gets used to it and stops having much of a reaction at all.
'When we travel to countries with lots of mosquitoes, it feels like we are getting bitten more than the locals,' says Logan. 'But we aren't – we're just reacting more.'
Can what you eat ward them off?
Over the years, studies have suggested that everything from drinking beer to smoking might make you a mosquito magnet. More recently, experts from Johns Hopkins University set up a trial in Zambia and discovered that the mosquitoes were consistently repelled by people with elevated levels of eucalyptol.
Eucalyptol is an aromatic component of many plants, and is found in the sort of ingredients many of us cook with: sweet basil, rosemary, sage and cardamom. One particular study subject had very elevated levels of eucalyptol and hardly any bites.
'We think this person likely obtained this compound from plant-based foods in their diet,' says a researcher, 'but it is also possible it could also have been from exogenous [external] products as eucalyptol is also a common ingredient in toothpaste and mouthwash.'
Logan is more sceptical. 'It is possible that plant essential oils have a repellent effect,' he says. 'But over years of research, I have never really been able to show anything you eat or drink [including garlic or beer] has any impact.'
Mosquitoes vs midges
Midges are much smaller than mosquitoes – they tend to be just a couple of millimetres whereas mosquitoes are about a centimetre, Prof Logan says.
'Mosquitoes have mouthparts that pierce the skin like a needle and you usually don't feel it. Midges have mouthparts that cut the skin which is why you feel them nip – they then feed from a pool of blood on your skin,' he adds.
Whilst midges tend to appear in high numbers (up to thousands), particularly on the west coast of Scotland, mosquitoes usually occur in smaller numbers.
How to control mosquitoes
Wear long trousers and socks. Mosquitoes are likely to strike at dawn and dusk, and you are most vulnerable below the knee.
Don't bother with citronella, as there is a dearth of evidence to support its use, or with anti-mosquito wristbands; one study showed that people wearing wristbands got bitten five times faster than those who sprayed their skin.
Use lemon eucalyptus and Deet repellent. Logan confirms that both work ('if you cover one of your arms in Deet and stick it in a box of mosquitoes you won't get bitten') and says the only problems arise from not reapplying enough. You also don't need 100 per cent Deet, as the concentration doesn't make it more effective, simply more long-lasting. A 30 per cent formulation is fine, so long as you reapply every few hours.
Also, try not to keep any stagnant water in your garden: pour out paddling pools in the late afternoon and empty buckets. 'Mosquitoes will breed in a bottle top with water in it,' says Logan. 'So you need to be vigilant.'
Use insect screens on your windows and doors to keep mosquitoes out, and ensure your home is well ventilated to avoid creating an attractive humid environment.
What are the best treatments for mosquito bites?
Oral antihistamine works but you need to start taking it a few days before your holiday, as it takes a while to have an effect.
There's no point sucking poison out, as there's no venom in a mosquito bite; instead try a block of ice to reduce swelling.
Or dab the area with either a mix of bicarbonate of soda and water or an antihistamine cream (which should calm a reaction but not as effectively as tablets).
Whatever you do, don't scratch. 'If you scratch, you can break the skin and let in bacteria,' says Logan. 'People have lost limbs from something as mild as scratching a mosquito bite.'