Mosquitoes
Mosquito bites: why do they itch, and what helps?
A mosquito bite is a small, red, itchy lump where a mosquito has bitten you. The itching and swelling usually clear up on their own within a few days (source: NHS). Holding something cold against it helps with the swelling and the itch. Below you can read why a mosquito bite itches, when to see a pharmacist or GP, and why mosquitoes bite some people more than others.
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How do you recognise a mosquito bite?
You recognise a mosquito bite by a small, red, itchy lump on skin that was uncovered, often after an evening outdoors or a night with the window open (source: NHS). There may be several lumps close together if a mosquito has bitten more than once. Strictly speaking a mosquito does not bite but pierces the skin with its mouthparts to drink blood. Only females do this, because they need blood to lay eggs (source: RIVM).
Why does a mosquito bite itch?
The itching and swelling are your body's reaction to the bite. When it bites, the mosquito leaves a little saliva in your skin, and your immune system reacts to it. How strong that reaction is differs from person to person: one person gets a small lump, another a large, warm swelling.
How long does a mosquito bite itch?
A mosquito bite usually itches for a few days at most: insect bites normally get better on their own within a few days (source: NHS). Try not to scratch, because scratching can make the skin break and become infected; cooling works better (see below).
Is a big swollen mosquito bite dangerous?
A big swollen mosquito bite is usually not dangerous: even a large lump almost always goes down on its own. Call 999 at once if, after a bite, you have swelling of the lips, mouth or throat, difficulty breathing, a fast heartbeat or you feel faint, because those are signs of a serious allergic reaction (source: NHS). See a GP, or call NHS 111, if the symptoms do not improve after a few days, if a large area around the bite becomes red and swollen, if there are signs of infection such as pus or increasing pain, or if you feel unwell after the bite (NHS).
What helps an itchy mosquito bite?
Cooling helps an itchy mosquito bite: hold a cold compress, such as a cloth soaked in cold water, or an ice pack wrapped in a towel against the bite for at least 10 minutes (source: NHS). It reduces swelling and itching. Also:
- Wash the area with soap and water first (NHS).
- Raise the area if it is swollen (NHS).
- Try not to scratch.
- Usually no medicine is needed. If the itching bothers you a lot, ask a pharmacist for advice; they can suggest something for itching or swelling (NHS).
Why do mosquitoes bite me more than other people?
Mosquitoes bite you more than other people because they choose by smell, and your smell is different from someone else's. Mosquitoes first find you by the carbon dioxide in your breath and your body heat; close up, they choose by the smell of your skin (source: RIVM). That smell comes largely from the bacteria that live on your skin, and those differ from person to person (research by Wageningen University). Sweat makes you more attractive too (RIVM). Light plays no part: according to RIVM, mosquitoes are not attracted to light.
Which other bites look like mosquito bites?
Itchy red lumps are also caused by fleas, bedbugs, ants and biting midges, among others (source: NHS). If you have bumps when there are no mosquitoes around, for example in the middle of winter, another creature may be to blame. Small black flies around your houseplants are fungus gnats; they do not bite. Read more in small black flies in the house.
How do you prevent mosquito bites?
You prevent mosquito bites by keeping mosquitoes out and covering or protecting your skin. Fly screens and a mosquito net keep mosquitoes out of your bedroom, and without standing water around the house fewer new mosquitoes appear (source: RIVM); our guide how to avoid mosquito bites explains how. The NHS advises covering exposed skin, for example with long sleeves and trousers, and using an insect repellent. On skin that stays uncovered, apply a mosquito repellent spray for your skin, as the label says.
Authorisation number of our mosquito spray in the UK: UK-2020-1247. Use biocides safely. Always read the label and product information before use.
Sources: NHS (insect bites and stings); RIVM, Dutch National Institute for Public Health and the Environment (mosquitoes); Wageningen University (skin smell and mosquitoes).
