Why do mosquitoes bite?
There are over 3,500 types of mosquitoes, but not all mosquitoes bite humans. Mosquito bites are caused by female mosquitoes piercing your skin with their needle-like mouth parts and feeding on your blood. They need your blood to help produce their eggs.
When they bite you – usually on humid summer nights – they inject saliva into your skin. Your body reacts to this saliva and gets small, red bumps that can be itchy. Usually these bites go away after a few days without needing any treatment.
But some people may get more serious symptoms like lots of swelling, itchiness, redness and pain, and may need medical treatment. And if you scratch them, mosquito bites may become infected, which means you’ll need to see a doctor and may need antibiotics.
Sometimes, mosquitoes in certain parts of the world carry serious infections like malaria and dengue – you’ll need to see a doctor if you get these diseases. In rare cases, some people may get a life-threatening allergic reaction to mosquito bites called anaphylaxis that needs emergency medical treatment.
What do mosquito bites look like?
Like many other insect bites, mosquito bites usually look like small, red bumps on your skin. There can be 1 bump, or more than 1 if you've been bitten a few times. You may see some swelling around the bites and they may also sting, feel very itchy, sore or warm. Sometimes, you may also get blisters where you’ve been bitten.
You may react differently than someone else does to a mosquito bite, or you may not have any reaction at all. Most people have mild symptoms – the small, red bumps usually appear quickly and go away without any treatment after a few days. Sometimes, the bites may only appear a few days after you’ve been bitten and take days or weeks to heal. And sometimes, you may only get symptoms after a few days or longer, which may be a sign that your bite is infected.
If you have a more serious reaction, your symptoms may include:
- swollen glands in your neck, armpits or groin
- an itchy, raised rash called hives (urticaria)
- a low fever – if you have a high fever, it may mean you have an infection
- a big area of swollen, red skin around the bite or bites
It’s rare but sometimes, mosquito bites may cause anaphylaxis, which needs emergency treatment in hospital.
Which diseases can you get from mosquito bites?
Mosquito bites are usually harmless. But in some parts of the world, mosquitoes can carry viral infections. And if these infected mosquitoes bite you, the viral infection may get passed on to you. Some of these diseases are more common than others, like malaria.
The infections mosquitoes can spread include:
- yellow fever
- Zika virus
- West Nile virus
- chikungunya virus
- encephalitis viruses – including Japanese encephalitis or La Crosse
If you’re going to a part of the world where you’re at risk of getting a mosquito-borne infection, it’s important to get medical advice before you travel. You may need to take medication or have vaccinations to stop you getting 1 of these diseases. Read more about travel vaccinations.
How to get rid of mosquito bites
Mosquito bites tend to get better on their own – usually within 3 to 10 days.
As soon as you get bitten, try these self-care measures:
- wash the area with soap and water to wash away the mosquito saliva, which causes symptoms like swelling and itchiness
- use cold compresses like an ice pack or a cold, damp cloth to help with any swelling
- take simple painkillers to help with pain – but speak to a pharmacist first on how to safely get and use these medicines
- don’t scratch your bites, as you could break your skin and bacteria from your hands could lead to a bacterial skin infection like cellulitis
Read more about the best treatment for insect bites.
How to stop mosquito bites itching
To relieve any itching, use an ice pack or cold, damp cloth to soothe your skin and try these treatments:
- rub calamine lotion on the bite area
- use a steroid cream like hydrocortisone cream
- take antihistamine medication to help with swelling and itchiness – speak to a pharmacist about which creams or tablets will work best for you
Treatment for infected mosquito bites
The treatment for an infected insect bite will depend on which infection you’ve got. Some conditions are more serious than others, so it’s important to get advice from a doctor as soon as possible.
Treatment options include:
- antibiotics if you’ve got cellulitis or other skin infections. Read more about the treatment for cellulitis
- antimalarial medication for malaria – it’s important to get treatment as soon as possible, as malaria can be life-threatening. But if the infection is treated early, most people get better. Read more about antimalarial medication
For diseases like dengue, yellow fever, Zika, chikungunya or encephalitis, there’s no cure. Treatment focuses on supporting your body until it can get rid of the infection. It includes resting at home, drinking lots of fluid and taking simple painkillers if you’re in pain or have a fever. But first speak to a pharmacist or doctor on how to safely get and use these medicines. For example, if you have dengue, you should only take paracetamol, as ibuprofen or aspirin may cause bleeding problems.
If these diseases make you very ill, you’ll usually need to go to hospital to get treatment like intravenous fluids through a drip in your arm (IV), oxygen or medication.
How to prevent mosquito bites
Mosquitoes tend to bite on hot summer nights. Try these tips to prevent them biting you:
- use air conditioning – mosquitoes don’t like cold rooms
- sleep under mosquito nets
- put mosquito nets or screens on your windows and doors
- don’t keep stagnant (still) water around, like water in buckets, as mosquitoes tend to collect around this water
- wear clothes that protect your skin like long-sleeved shirts and trousers. You can also treat your clothes with a chemical called permethrin or buy clothes treated with this chemical. But don’t apply this chemical directly to your skin
- use insect repellent – try ones that contain an ingredient called DEET
When to see a doctor about mosquito bites
Call an ambulance immediately if you have any signs of anaphylaxis, including:
- trouble breathing (wheezing)
- your face, mouth or throat swelling up
- feeling sick (nausea) or being sick (vomiting)
- trouble swallowing
- feeling faint, dizzy or fainting
You’ll need treatment in hospital for anaphylaxis, including oxygen, fluids and medicines like adrenaline or steroids. When you go home, you'll usually be given an emergency injection that contains adrenaline. Carry it with you at all times so you can use it in case of an emergency.
Sometimes, a mosquito bite can get infected or you might have picked up a mosquito-borne disease. See a doctor urgently if you’ve been bitten by a mosquito and:
- the area around the bite is getting bigger, more red, sore and warm
- have a fever
- after a few days, your symptoms aren’t getting better
- have a new rash
- you feel like you have the flu
- have muscle and joint pain
- have a sore tummy or poo that’s very watery
- have headaches
- your skin or the whites of your eyes are yellow (jaundice)
- your neck hurts when you move it
- have trouble speaking or moving parts of your body
- the bites are in your mouth or throat, or near your eyes
See a doctor if you’ve been in an area where mosquitoes carry diseases and you don’t feel well, even if it’s months later. This is because you won’t always realise you’ve been bitten, as it usually happens at night when you’re sleeping and you may not get any symptoms. With some infections like malaria, symptoms may only appear up to 1 year later.
You should also see a doctor if you’re pregnant or planning to get pregnant and you’ve travelled to or live in an area where Zika is found, as it can affect your developing baby. Sometimes, you’ll have no or only very mild symptoms, so you might not know you've caught this disease either.
Your health questions answered
Why do my mosquito bites get so big?Answered by: Healthily's medical team
Everyone's body is different and reacts differently. The first time you’re bitten, you usually don’t get a reaction. But after this first bite, your body will recognise the toxins in a mosquito's saliva and you may get more obvious symptoms. Some people may have a more serious reaction like a large area of redness around the bite, as their bodies have had a stronger reaction to this saliva. And if you have conditions like HIV or cancer, you may have a more serious reaction too. If you get a skin infection from scratching the bites, your bites may get very big and this red, swollen area may keep spreading. See a doctor if you’re worried about your mosquito bites.
- most mosquito bites are harmless and you’ll have mild symptoms, which usually go away in 3 to 10 days
- mosquito bites usually look like small, red bumps, and they can itch a lot
- mosquito bites usually go away by themselves without any treatment
- if your bites are very itchy, use cold compresses, steroid creams and antihistamines to get rid of the itchiness
- prevent mosquito bites by using insect repellent, covering up your skin and sleeping under mosquito nets