Some people can sit outside all evening and barely earn a nibble. Others step into the garden for five minutes and return looking as if they have been used as a buffet.

The difference is familiar, frustrating and often blamed on everything from “sweet blood” to blood type.

Now, a large and unusually lively study carried out at a Dutch music festival suggests that mosquitoes may be especially interested in people who drink beer, skip sunscreen and share a bed or tent.

The research, posted as a preprint on bioRxiv and not yet peer reviewed, comes from the Mosquito Magnet Trial, a pop-up science experiment run at the Lowlands Festival in the Netherlands in August 2023. Researchers tested mosquito attraction in 465 adult festivalgoers using a custom-built cage that let mosquitoes smell a participant’s arm but not bite it.

The study found that mosquitoes landed more often near the arms of people who had drunk beer in the previous 12 hours. Participants who had slept next to someone else the night before were also more attractive to mosquitoes. Sunscreen, however, appeared to reduce mosquito attraction, especially when it had been applied to the forearm after a recent shower.

The findings are colourful, and the setting was anything but ordinary. The study was conducted inside connected shipping containers at a hot, crowded festival, among people whose diet, hygiene, sleep and alcohol intake were unlikely to resemble an average weekday.

Still, the trial is notable for its size. Many earlier studies on human attractiveness to mosquitoes have involved small numbers of volunteers under tightly controlled laboratory conditions. This one tested hundreds of people in a messy, real-life environment.

That messiness is both its charm and its weakness.

A pop-up mosquito lab at a music festival

The trial took place during Lowlands, a three-day festival attended by around 65,000 people. Festivalgoers who visited the science area were invited to take part in a 20-minute study. They answered anonymous questions about their hygiene, diet, alcohol use, drug use, sunscreen, perfume and sleeping arrangements. Researchers also measured their ear temperature and used a breathalyser to estimate alcohol levels.

Then came the mosquito test.

Participants placed their lower right arm against one side of a transparent acrylic cage containing 20 to 35 female Anopheles stephensi mosquitoes, a malaria-carrying mosquito species often used in laboratory research. The cage had tiny perforations that allowed skin odours to pass through but stopped mosquitoes from biting. On the opposite side of the cage was a sugar feeder, giving mosquitoes a competing attraction.

Before presenting their arm, participants blew into the cage for 10 seconds. This mattered because mosquitoes use carbon dioxide from human breath as an early signal that a potential host is nearby. Once activated, they rely on other cues, including smell, body heat, moisture and visual signals.

For three minutes, a camera under the cage recorded mosquito movement. Researchers later used video-tracking software to count how often mosquitoes landed near the participant’s arm compared with other areas of the cage.

The mosquitoes were not allowed to feed on blood. In other words, this was a test of attraction, not actual biting.

Beer drinkers drew more mosquito attention

The most striking result was linked to beer. People who reported drinking at least one beer in the previous 12 hours attracted significantly more mosquito landings than those who had not drunk beer.

In the final model, beer drinkers were about 35% more attractive to mosquitoes than non-beer drinkers. The result remained statistically significant after researchers adjusted for multiple testing and considered other factors.

This finding supports earlier smaller studies suggesting that beer consumption may increase mosquito attraction. One previous study in Burkina Faso found that beer increased attractiveness to malaria mosquitoes. Another study also reported greater mosquito attraction after alcohol intake.

Yet the new study adds an interesting twist. Breathalyser results did not show a clear link between measured alcohol concentration and mosquito attraction. That means alcohol in the bloodstream itself may not be the direct cause. Instead, beer drinking could be a marker for something else.

Possibilities include:

• odour compounds linked to beer consumption;
• changes in skin chemistry after drinking;
• behaviour associated with beer drinking, such as more social contact;
• diet, sweating or time spent outdoors;
• other festival habits that were not fully measured.

The researchers raise the possibility that mosquitoes may be responding to the distinctive smell profile of beer drinkers rather than alcohol itself. That does not mean one pint will turn everyone into a mosquito magnet. It does suggest that what we eat and drink may subtly alter the chemical signals our bodies give off.

Sunscreen appeared to reduce attraction

The study also found that sunscreen use on the forearm was linked with fewer mosquito landings. The effect was strongest among people who had showered within the previous six hours.

In that group, those who had applied sunscreen to the forearm were roughly half as attractive to mosquitoes as those who had not used sunscreen. The protective association became weaker as more time passed since the last shower.

This may mean sunscreen masks human skin odours that mosquitoes normally use to find us. It may also mean some sunscreen ingredients have a mild repellent effect. The study did not record sunscreen brands, ingredients or exact application times, so it cannot identify what caused the effect.

It is also important not to treat sunscreen as a substitute for mosquito repellent. Sunscreen is designed to reduce ultraviolet damage, not to prevent insect bites. In areas where mosquitoes transmit diseases such as malaria, dengue, Zika or chikungunya, proven repellents remain important. Products containing DEET, icaridin, IR3535 or oil of lemon eucalyptus are commonly recommended by public health bodies, depending on location and individual suitability.

Still, the sunscreen finding is practical and intriguing. Many people already apply sunscreen during outdoor events. If some formulations also reduce mosquito interest, that could be useful for future prevention research.

Sharing a bed or tent was linked with more attraction

Another notable finding was that people who had slept next to someone else the previous night were more attractive to mosquitoes than those who slept alone. In the final analysis, this was associated with a 34% increase in mosquito attraction.

The study cannot say why. Shared sleeping may change a person’s scent through close physical contact. It could also reflect other behaviours. People who share a tent or bed at a festival may differ in alcohol intake, activity levels, hygiene, sweating, perfume use or time spent in crowded spaces. Although the researchers tested for an interaction between beer drinking and bed-sharing and did not find one, many unmeasured factors could still play a part.

The result should not be overinterpreted. It does not mean sleeping next to someone directly causes mosquito attraction. It means that, in this study population, the two were associated.

What about blood type and perfume?

The study did not find convincing evidence that blood type influenced mosquito attraction. That matters because blood type is one of the most common explanations people give for why they are bitten more often. Previous research on blood type and mosquito preference has produced mixed results, and this study does not support blood type as a major factor.

Perfume also did not show a clear effect, whether applied to the forearm or elsewhere. That may surprise people who assume fragrance always attracts or repels insects.

At a festival, however, the background cloud of smells is likely to be complex: sweat, sunscreen, food, alcohol, soil, smoke, toilets, tents and thousands of bodies in summer heat. In that environment, perfume may simply be one scent among many.

Skin bacteria may play a role, but the signal was modest

Researchers also collected forearm skin swabs from selected participants to study their skin microbiome — the community of bacteria and other microbes living on the skin. Skin microbes matter because they help produce many of the odours mosquitoes detect.

The team compared people with the highest and lowest mosquito attraction scores. They did not find a significant difference in overall microbial diversity. Nor did the overall skin microbiome composition clearly separate high-attraction from low-attraction participants.

However, one bacterial group, Streptococcus, was more abundant in highly attractive individuals. The difference was modest and only statistically significant before correction for multiple testing, meaning it should be treated as a clue rather than a firm conclusion.

Other studies have linked mosquito attraction with skin microbes, including bacteria that produce odour-related compounds. Some research has suggested that people who are highly attractive to mosquitoes may have different levels of certain skin acids or a less diverse skin microbiome. The new festival study adds to that picture but does not settle it.

One challenge is that festival conditions are not microbiome-friendly from a research control point of view. Participants may have showered, sweated, used sunscreen, shared tents, touched surfaces, danced for hours, changed clothes irregularly, visited saunas or eaten unusual foods. All of this could affect skin bacteria.

Why mosquitoes choose some people more than others

Mosquito attraction is not controlled by a single factor. It is a layered process.

First, mosquitoes detect carbon dioxide from breath. This tells them that an animal or human may be nearby. Then they use a mix of signals to close in. These include:

• body odour;
• skin chemicals;
• heat;
• moisture;
• visual contrast;
• movement;
• possibly microbial by-products on the skin.

Different mosquito species may also prefer different cues. The species used in this study, Anopheles stephensi, is an important malaria vector in parts of the world, but results may not apply perfectly to all mosquitoes. The mosquitoes that ruin a barbecue party in Kuala Lumpur or bite near a Langkawi beach may respond somewhat differently.

Even so, understanding mosquito preference matters. In regions where mosquitoes spread disease, people who are bitten more often may face greater infection risk. If scientists can identify reliable factors that increase or reduce attraction, that could inform better repellents, odour-based traps or public health advice.

The study’s strengths

The trial has several strengths. First, it included 465 participants, making it large compared with many previous mosquito-attraction studies. Second, it used a standardised experimental setup for all participants. Third, mosquitoes could smell participants without biting them, which made the test safer and more acceptable in a public setting.

The researchers also used video tracking rather than relying only on human observation. That allowed them to quantify mosquito landings more systematically. They accounted for mosquito activity in the cages, which was important because mosquitoes can become less responsive over time, especially in warm or stressful conditions.

Finally, the study captured real-life variation. People were not asked to follow strict rules about washing, diet or product use beforehand. That makes the results relatable, even if it also makes cause and effect harder to prove.

The limitations are important

This was not a controlled clinical trial. It was an observational study in a festival setting. That means it can identify associations, but it cannot prove that beer, bed-sharing or sunscreen directly caused changes in mosquito attraction.

There was also selection bias. Participants were festivalgoers who chose to take part in a science activity. They may not represent the wider population. Their behaviour during the festival may not reflect normal habits.

Many variables were self-reported. People may misremember how much they drank, when they showered or what they used on their skin. Some may underreport drug use or alcohol intake. Blood type was also self-reported and not confirmed by testing.

The mosquito assay measured attraction over just three minutes. It counted landings near an arm through a cage, not actual bites in a natural outdoor setting. Mosquitoes were offered a choice between a human arm and a sugar feeder, which is not the same as a real-world encounter at dusk.

The microbiome analysis was performed on a selected subset of participants, not the full group. That makes it useful for exploration but less definitive.

The preprint status also matters. Because the study has not yet gone through peer review, its methods, analysis and interpretation may change after scrutiny by independent experts.

What should readers do with this information?

For everyday life, the findings are interesting but should be used with caution. If you are camping, attending a festival or spending time outdoors, the evidence still supports familiar bite-prevention steps:

• use a proven mosquito repellent when needed;
• wear long sleeves and trousers in high-risk areas;
• sleep under insecticide-treated nets where mosquito-borne disease is present;
• remove standing water around homes;
• use window screens or air conditioning where available;
• apply sunscreen for sun protection, but do not rely on it as your only anti-mosquito measure.

If you are especially prone to bites, it may be worth noticing whether alcohol, sweating, skincare products or social settings seem to affect your own experience. But there is no need to cancel your holiday plans or swear off beer solely because of this study.

The bigger message is that human scent is highly individual. Mosquitoes are reading a chemical signature we barely notice. That signature can shift with microbes, hygiene, diet, products on the skin and behaviour.

Why this research matters

The Mosquito Magnet Trial turns a familiar annoyance into a serious scientific question. Why do mosquitoes target some people more than others?

Its festival setting gives the study a memorable edge, but the issue is more than a seasonal nuisance. Mosquito bites are a route for some of the world’s most important infectious diseases.

This preprint suggests that beer drinking, recent social sleeping and lack of sunscreen may be linked with greater mosquito attraction, while sunscreen on recently washed skin may reduce it. The findings are not final proof, but they offer useful clues for future research into odour, skin chemistry and mosquito behaviour.

For now, the practical takeaway is simple. Mosquitoes do not choose at random. They follow signals. The better scientists understand those signals, the closer we get to smarter ways of preventing bites — whether at a festival campsite, in a back garden or in places where mosquito-borne disease is a daily threat.