How to know what’s bitten you
A sudden red and itchy lump on your skin is often a sign that an insect, or bug, of some kind has bitten you.
It can happen when you’re outside in nature or at home, and you may sometimes feel a small, sharp pain as it happens.
There are many different types of insect bites and the most common offenders are mosquitoes, midges, ticks, horseflies, bedbugs, fleas, mites, ants and spiders (which are technically arachnids, not insects). And during the summer, most of these insects and spiders are out in greater numbers.
Why and how do insects bite?
Bugs bite by piercing a hole into your skin to feed on your blood. When they do this, they release saliva that can cause the skin around the bite to become swollen, red and itchy.
Most insect bites are nothing to worry about and get better within a few hours or days, but they can sometimes cause an allergic reaction or even spread infectious diseases, such as malaria, dengue fever or Lyme disease.
The treatment for most insect bites is similar – focusing on relieving itching or swelling. But it can be useful to know which insect has bitten you to prevent further bites from happening and to work out if you need to see a doctor.
How to identify the different types of common insect bites
Mosquito bites usually leave small, red lumps on your skin that are very itchy. Some people develop blisters filled with fluid.
These conditions are more common across Asia, Africa and South America and occur less in the UK, Europe or North America. But some of them, like dengue fever and Zika, have spread locally in regions such as the south of France and Spain in recent years.
You should see a doctor immediately if you develop these symptoms following a mosquito bite:
You may not feel a tick bite as they’re not always painful, but ticks can feed on your body for many days before dropping off. So if you’re in an area that has ticks, it’s important to check your skin regularly – and remove any ticks safely as soon as possible.
If a tick has bitten you, you may get a small red lump and the area around the bite may become itchy, swollen or bruised. It may also form a blister.
Most tick bites heal within 3 weeks, but some bites can cause a serious bacterial infection called Lyme disease, depending on where you are. Ticks that carry Lyme disease are more common in the forests of Asia, parts of the UK and Europe and the US.
If Lyme disease isn’t treated, it can be serious, so you should see a doctor if you get:
- a pink or red circular rash around the area of the tick bite that looks like a ‘bull’s eye’ on a dartboard
- a temperature of 38C or over
Bites from a horsefly can be very painful, as these insects cut your skin when biting you, rather than piercing it.
Their bites can cause your skin to become red and raised and may cause an infection. They also take a long time to heal. Other symptoms of horsefly bites include:
- a large red, raised rash (hives)
- parts of your body becoming puffy or swollen
If you have signs of an infected insect bite or the bites become more painful, red or swollen, you should see a doctor.
Midge or gnat bites
A midge is a small fly and its bites look similar to mosquito bites – small, red lumps that can be painful or itchy, or both. Some people develop blisters from these bites.
Bedbugs live on furniture or bedding and their bites can be very itchy, but they don’t usually cause other health issues.
Bedbugs usually bite exposed areas of the body, such as your face, neck, arms or hands and you may see many bites in a straight line or zigzag pattern across your skin.
These bumps can be itchy and red and sometimes cause painful swelling. For some people, bites can result in a severe allergic reaction (anaphylaxis), but this is rare.
Mites are small insects that cause very itchy red lumps to develop after they bite you and these can become blisters.
They usually bite skin that’s not covered up, for example, by clothing. But if the mites have come from your pet, you may get bitten on your tummy or thighs if your pet’s been sitting on your lap.
Some mites burrow into your skin and cause scabies, which can then spread across your body.
Signs of scabies to look out for include:
- silvery lines on your skin with a dot at one end (where the mites have burrowed and laid eggs in your skin)
- a rash that soon spreads across your body, often starting between your fingers
- the rash turning into tiny red spots
If you think you have scabies, you should see a doctor immediately.
Fleas from animals such as cats and dogs often bite humans. Their bites can sometimes develop into blisters.
Like bedbugs, flea bites also cause small itchy red lumps grouped in lines or clusters, but the bites are often found below the knee – usually around the ankles.
If you have a pet and carry them regularly, you may see bites on your arms.
Ants that bite humans include red ants, wood ants and flying ants.
Ant bites are usually harmless, leaving a pale pink mark on your skin. Sometimes the area can become painful, itchy or swollen.
If you experience any serious symptoms following any kind of insect bite, you should see a doctor. Otherwise, most bites go away on their own. Any symptoms such as pain or itching can be treated with creams, ointments or painkillers, such as paracetamol – speak to a pharmacist about how to safely get and use these medicines.
Most spiders aren’t dangerous, but some may give you a painful bite.
Signs of a spider bite include a small puncture mark on your skin, redness, swelling and pain, but some bites can become infected and, in rare cases, cause anaphylaxis.
Severe symptoms may include feeling sick, sweating, dizziness, nausea and vomiting. If you experience any of these serious symptoms, see a doctor immediately.
When to see a doctor about insect bites
Call an ambulance immediately if you get any symptoms of anaphylaxis, as it can be life-threatening. These include:
- trouble breathing
- your face, mouth, lips, tongue, throat and airways swelling up
- a fast heart rate
- dizziness or feeling faint (or fainting)
- tummy pain
- feeling sick (nausea)
- skin redness
- feeling like something very bad is going to happen
Anaphylaxis usually happens within a few minutes of being stung or bitten, but it can sometimes happen later. So still call an ambulance if you notice any of the symptoms above, even if it’s been a few hours or longer since you were bitten or stung.
If you’ve been bitten or stung by an insect or spider, see a doctor as soon as possible if:
- your symptoms haven’t got better after a few days or they’re getting worse
- you’re worried about your symptoms
- the swelling and redness involves a large area (more than about 10cm) or it’s spreading
- the bite or sting and the area around it is getting more painful, red and swollen
- you see pus in or around the bite or sting
- you were bitten or stung near your eyes or in your throat or mouth
- you get a circular rash, which looks like a ‘bull’s eye’ on a dartboard, around the bite or sting
- you have swollen glands, a high temperature and you feel generally unwell
Your health questions answered
What type of insect bites cause swelling?Answered by: Healthily's medical team
When some insects and spiders bite you, they inject a poison called formic acid into your skin, which can cause swelling, redness, pain, itching and other symptoms. This includes insects like midges and gnats, ticks and horseflies. And sometimes, if your bite gets infected, it may cause your skin and your glands to swell up too. See a doctor if the bite and the area around it is getting more painful, hot, red and swollen. You should also see a doctor if the swelling and redness is affecting a large area on your skin (more than 10cm) or it’s spreading. It’s rare, but sometimes your face, mouth, lips, tongue, throat and airways may swell up after you’ve been bitten or stung. This is a sign of the severe allergic reaction anaphylaxis – call an ambulance immediately, as it can be life-threatening.
- you’re most likely to get bitten by mosquitoes, midges, ticks, horseflies, bedbugs, fleas, mites, ants and spiders
- most insect bites or stings get better within a few hours or days, but they can sometimes cause an allergic reaction or even spread infectious diseases, such as malaria
- tick bites usually heal within 3 weeks, but some bites can cause a serious bacterial infection called Lyme disease
- the treatment for most insect bites is similar and focuses on relieving itching and swelling at home, but sometimes you may need to see a doctor if you’ve had a serious allergic reaction or get an infection
- call an ambulance immediately if you get any symptoms of the severe allergic reaction anaphylaxis, as it can be life-threatening