If you have ever felt that mosquitoes prefer you over everyone else at a barbecue, you may well be right. Mosquitoes do not bite randomly — they use a sophisticated array of sensory cues to locate and select their hosts. Understanding what attracts mosquitoes to certain people can help explain why some individuals seem to be mosquito magnets and inform strategies for reducing bites.
The Sensory Journey: How Mosquitoes Find You
Female mosquitoes (only females bite, as they need blood protein to develop their eggs) locate hosts through a sequential series of sensory cues that operate at different distances:
- Long range (10–50 metres): Carbon dioxide. Mosquitoes detect the CO2 plume in exhaled breath using specialised receptors on their maxillary palps. Humans exhale approximately 200 ml of CO2 per minute, creating a detectable plume that mosquitoes follow upwind.
- Medium range (5–15 metres): Visual cues. Once activated by CO2, mosquitoes use vision to locate dark-coloured, moving objects. People wearing dark clothing are more visible to mosquitoes than those in light colours.
- Short range (1–2 metres): Body heat and moisture. At close range, mosquitoes detect the warmth and humidity emanating from the skin using heat-sensitive receptors on their antennae.
- Contact range: Skin chemicals. On landing, mosquitoes taste the skin surface with receptors on their legs and mouthparts, assessing a cocktail of chemicals including lactic acid, ammonia, and carboxylic acids before deciding to bite.
Key Attraction Factors
| Factor | Effect on Attraction | Evidence Strength |
|---|---|---|
| Carbon dioxide output | Higher CO2 = more attractive (larger people, pregnant women, those exercising) | Strong |
| Body odour/skin bacteria | Specific bacterial communities produce more attractive volatile compounds | Strong |
| Blood type | Type O may be slightly more attractive than Type A in some studies | Moderate (species-dependent) |
| Body heat | Higher skin temperature increases attractiveness | Strong |
| Lactic acid | Produced during exercise; significant attractant | Strong |
| Clothing colour | Dark colours (black, navy, red) more attractive than light colours | Moderate |
| Alcohol consumption | Drinking beer increases attractiveness (possibly via skin chemical changes) | Moderate |
| Pregnancy | Pregnant women exhale more CO2 and have higher body temperature | Strong |
The Role of Skin Bacteria
One of the most significant factors determining individual attractiveness to mosquitoes is the composition of skin microbiota. Research published in PLOS ONE found that people with a lower diversity of skin bacteria but a higher abundance of certain species (particularly Staphylococcus spp.) were significantly more attractive to the malaria mosquito Anopheles gambiae. Conversely, people with a more diverse skin bacterial community were less attractive.
The bacteria on human skin metabolise components of sweat to produce volatile organic compounds — the specific blend of which creates each person's unique body odour. Mosquitoes have evolved to detect and respond to particular components of this chemical signature.
Why Do Mosquito Bites Itch?
- When a mosquito bites, she injects saliva containing anticoagulants and proteins that prevent blood clotting
- The human immune system recognises these foreign proteins and releases histamine
- Histamine causes the blood vessels near the bite to swell, producing the characteristic itchy red bump
- Repeated exposure to mosquito saliva can lead to either increased sensitivity (worse reactions) or tolerance (reduced reactions) over time
Did you know? Mosquitoes are the deadliest animals on Earth. Through the transmission of diseases including malaria, dengue fever, Zika virus, and yellow fever, mosquitoes are responsible for an estimated 700,000 human deaths per year worldwide. In the UK, mosquitoes are primarily a nuisance rather than a disease vector, though climate change is expanding the range of disease-carrying species into temperate Europe.
How to Reduce Mosquito Bites
Based on the science of mosquito attraction, the following strategies are most effective:
- Use DEET-based repellents: DEET (N,N-diethyl-meta-toluamide) remains the gold standard insect repellent. It works by blocking the mosquito's ability to detect skin odours and CO2. Concentrations of 20–30% provide several hours of protection.
- Wear light-coloured clothing: Light colours are less visible to mosquitoes and also reflect more heat, keeping skin cooler.
- Cover exposed skin: Long sleeves and trousers provide a physical barrier, especially at dawn and dusk when many species are most active.
- Avoid peak activity times: Most mosquito species in the UK are most active at dawn and dusk.
- Eliminate standing water: Mosquitoes breed in even small volumes of standing water. Empty saucers, blocked gutters, water butts (cover with mesh), and any other water-collecting containers.
- Use fans: Mosquitoes are weak fliers. A fan on a patio or by an open window disrupts their flight and disperses the CO2 plume that guides them to you.
Do Mosquito Repellent Devices Work?
| Method | Effectiveness | Notes |
|---|---|---|
| DEET-based repellent | Highly effective | Apply to exposed skin; reapply as directed |
| Picaridin (icaridin) | Highly effective | Good alternative to DEET; less odour |
| Citronella candles | Minimal effect | Only effective within a very small radius |
| Ultrasonic devices | No evidence of effectiveness | Multiple studies have found no repellent effect |
| Mosquito coils | Moderately effective | Smoke can be irritating; use outdoors only |
| Permethrin-treated clothing | Effective | Kills mosquitoes on contact; lasts through multiple washes |
Key Takeaway
Mosquitoes locate human hosts through a sequence of cues: carbon dioxide at long range, visual and thermal cues at medium range, and skin chemicals at close range. Individual attractiveness varies based on CO2 output, skin bacterial composition, body heat, and other factors. The most effective protection combines DEET or picaridin-based repellents with light-coloured, long-sleeved clothing and the elimination of standing water breeding sites.