An insect bite or sting often causes a small lump to develop, which is usually very itchy. A small hole, or the sting itself, may also be visible, along with a weal.
An insect bite or sting often causes a small lump to develop, which is usually very itchy.
A small hole, or the sting itself, may also be visible. The lump may have an inflamed (red and swollen) area around it that may be filled with fluid. This is called a weal.
Insect bites and stings usually clear up within several hours and can be safely treated at home.
The symptoms that can occur from different types of insect bites are described below.
Midges, mosquitoes and gnats
Bites from midges, mosquitoes and gnats often cause small papules (lumps) to form on your skin that are usually very itchy. If you're particularly sensitive to insect bites, you may develop:
- bullae – fluid-filled blisters
- weals – circular, fluid-filled areas surrounding the bite
Mosquito bites in certain areas of tropical countries can cause malaria.
Flea bites can be grouped in lines or clusters. If you're particularly sensitive to flea bites, they can lead to a condition called papular urticaria, where a number of itchy red lumps form. Bullae may also develop.
Fleas from cats and dogs can often bite below the knee, commonly around the ankles. You may also get flea bites on your forearms if you've been stroking or holding your pet.
A bite from a horsefly can be very painful. As well as the formation of a weal around the bite, you may also experience:
- urticaria – a rash of weals (also called hives, welts or nettle rash)
- angio-oedema – itchy, pale pink or red swellings that often occur around the eyes and lips for short periods of time
Horseflies cut the skin when they bite, rather than piercing it, so horsefly bites can take a long time to heal and can cause an infection.
Bites from bedbugs aren't usually painful, and if you've not been bitten by bedbugs before, you may not have any symptoms.
If you have been bitten before, you may develop intensely irritating weals or lumps.
Bedbug bites often occur on your:
Read more about bedbugs.
The Blandford fly
The Blandford fly (sometimes called blackfly) is usually found near rivers. It's common in:
- East Anglia
However, there have also been reports of Blandford fly bites occurring in other areas of England.
You're most at risk of being bitten by a Blandford fly in May and June. Bites often occur on the legs and are very painful.
They can produce a severe localised reaction (a reaction confined to the area of the bite) with symptoms such as:
- a high temperature of 38C (100.4F) or over
- joint pain
Tick bites aren't usually painful and sometimes only cause a red lump to develop where you were bitten. However, in some cases they may cause:
Ticks can carry a bacterial infection called Borrelia burgdorferi, which causes Lyme disease. Lyme disease can be serious if it isn't treated.
Mites cause very itchy lumps to develop on the skin and can also cause blisters. If the mites are from pets, you may be bitten on your abdomen (tummy) and thighs if your pet has been sitting on your lap. Otherwise, mites will bite any uncovered skin.
Spider bites from spiders native to the UK are rare. You're more likely to be bitten by a spider while you're abroad, if you keep non-native spiders as pets, or if you have a job that involves handling goods from overseas.
Spider bites leave small puncture marks on the skin, which can be painful and cause redness and swelling.
In severe cases, a spider bite may cause nausea, vomiting, sweating and dizziness. Very rarely, a spider bite may cause a severe allergic reaction.
Wasps and hornets
A wasp or hornet sting causes a sharp pain in the area that's been stung, which usually lasts just a few seconds.
A swollen red mark will often then form on your skin, which can be itchy and painful.
A bee sting feels similar to a wasp sting, but the sting and a venomous sac will be left in the wound. You should remove this immediately by scraping it out using something with a hard edge, such as a bank card.
Don't pinch the sting out with your fingers or tweezers because you may spread the venom.
Most people won't have severe symptoms after being bitten or stung by an insect, but some people can react badly to them because they've developed antibodies to the venom.
You're more likely to have an allergic reaction if you're stung by an insect. The reaction can be classed as:
- a minor localised reaction – this is normal and doesn't require allergy testing, although the affected area will often be painful for a few days
- a large localised reaction (LLR) – this can cause other symptoms, such as swelling, itching and a rash
- a systemic reaction (SR) – this often requires immediate medical attention because it can cause a potentially life-threatening allergic reaction (anaphylaxis)
Although insect bites and stings are a common cause of anaphylaxis, it's rare to experience anaphylaxis after an insect sting, and it's rarely fatal.
Large localised reactions and systemic reactions are described in more detail below.
Large localised reaction (LLR)
If you have a large localised reaction (LLR) after being bitten or stung by an insect, a large area around the bite or sting will swell up. The area may measure up to 30cm (12in) across, or your entire arm or leg could swell up.
The swelling will usually last longer than 48 hours, but should start to go down after a few days. This can be painful, but the swelling won't be dangerous unless it affects your airways.
If you're bitten or stung many times by one or more insects, your symptoms will be more severe because a larger amount of venom will have been injected.
You may have an LLR several hours after being bitten or stung. This could include:
- a rash
- painful or swollen joints
Systemic reaction (SR)
You're more likely to have a systemic reaction (SR) if you've been bitten or stung before and become sensitised, particularly if it was recently. People who've been sensitised to bee stings are more likely to have an SR than people who are stung by wasps.
Dial 999 immediately to request an ambulance if you've been bitten or stung and have any of the following symptoms:
- wheezing, hoarseness or difficulty breathing
- nausea, vomiting or diarrhoea
- a fast heart rate
- dizziness or feeling faint
- difficulty swallowing (dysphagia)
- a swollen face or mouth
- confusion, anxiety or agitation
It's rare for an SR to be fatal, particularly in children, although someone with an existing heart or breathing problem is at an increased risk.
Read about treating insect bites and stings.
Most insect bites and stings cause small local reactions where the symptoms can be easily treated. If your symptoms are severe, see your GP.
Most insect bites and stings cause small reactions that are confined to the area of the bite (localised reactions). They can usually be treated at home.
However, see your GP as soon as possible if your symptoms are severe.
Removing a sting
As soon as you've been stung by a bee, remove the sting and venom sac if it's been left in your skin. Do this by scraping it out, either with your fingernails or something with a hard edge, such as a bank card.
When removing the sting, be careful not to spread the venom further under your skin and don't puncture the venom sac.
Don't pinch the sting out with your fingers or a pair of tweezers because you may spread the venom. If a child has been stung, an adult should remove the sting.
Wasps and hornets don't usually leave the sting behind, so they could sting you again. If you've been stung and the wasp or hornet is still in the area, walk away calmly to avoid being stung again.
Most insect bites and stings cause itching and swelling that usually clears up within several hours.
Minor bites and stings can be treated by:
- washing the affected area with soap and water
- placing a cold compress (a flannel or cloth cooled with cold water) over the affected area to reduce swelling
- not scratching the area as it can become infected (keep children's fingernails short and clean)
See your GP if the redness and itching gets worse or doesn't clear up after a few days.
If the bite or sting is painful or swollen, you can also:
- wrap an ice pack, such as a bag of frozen peas, in a towel and place it on the swelling
- take painkillers, such as paracetamol or ibuprofen (children under 16 years of age shouldn't be given aspirin)
- use a spray or cream that contains local anaesthetic, antihistamine or mild hydrocortisone (1%) on the affected area to prevent itching and swelling
- take an antihistamine tablet to help reduce swelling (antihistamine tablets are available on prescription or from pharmacies)
If local swelling is severe, your GP may prescribe a short course of oral corticosteroids, such as prednisolone, to take for three to five days.
If you have an allergic reaction after being bitten or stung, even if it's just a skin rash (hives), your GP may prescribe an adrenaline pen (an auto-injector) and show you how to use it. You'll also be referred to an allergy clinic for further tests and treatment.
If you develop blisters after being bitten by an insect, don't burst them because they may become infected.
Blisters don't usually cause pain unless they rupture (burst) and expose the new skin underneath. If possible, use an adhesive bandage (plaster) to protect the blistered area.
See your GP if the bite or sting fills with pus and feels tender to touch, your glands swell up and you feel unwell with flu-like symptoms.
Your GP may prescribe oral antibiotics (medicines to treat infections caused by bacteria). You'll need to take these as instructed, usually two to four times a day for seven days.
Dial 999 to request an ambulance if you have swelling or itching anywhere else on your body after being bitten or stung, or if you're wheezing or have difficulty swallowing. You'll need emergency medical treatment.
If you have the symptoms of a systemic reaction (SR), it could lead to anaphylactic shock. Anaphylaxis may need to be treated with an adrenaline injection, antihistamines, oxygen or an intravenous drip directly into a vein.
If previous insect bites or stings have caused a large skin reaction, such as redness and swelling more than 10cm (4 inches) in diameter, your GP may refer you to an allergy clinic.
The criteria for referring someone to an allergy clinic may vary depending on what's available in your local area.
Immunotherapy (desensitisation or hyposensitisation) is a possible treatment option if you're allergic to wasp or bee stings.
It involves being injected with small doses of venom every week to alter your body's immune response to venom.
You need to be observed after each injection to make sure you don't have an allergic reaction to the treatment.
Over time, your body becomes used to the venom (desensitised) and you're no longer at risk of anaphylaxis.
When a high enough dose has been reached, the injections are given at four to six-week intervals for a further two to three years.
Your allergist (allergy specialist) will decide how much venom is injected and how long the injections need to continue for. This will depend on your initial allergic reaction and your response to the treatment.
For more information about immunotherapy, see treating allergies.
If you've been bitten by a tick, remove it as soon as possible to reduce the risk of getting a tick-borne infection, such as Lyme disease (a bacterial infection that causes a pink or red circular rash to develop around the area of the bite).
It's important that you remove the tick quickly and correctly by:
- using a pair of fine-tipped tweezers or a tick removal tool (available from pet shops or veterinary surgeries)
- wearing gloves or using tissue over your fingers to avoid touching the tick
- grabbing the tick as close to the skin as possible
- gently but firmly pulling straight up until all of the tick's mouthparts have been removed
- not twisting or jerking the tick while removing it to avoid the mouthparts breaking off and remaining in the skin
- washing your hands with soap and water afterwards
Don't use petroleum jelly, alcohol, a lit match or any other method to try to remove a tick. It won't work and could cause infection.
After removing the tick, clean the bite with soap and water or an antiseptic, such as an iodine scrub.
Avoid scratching the bite because it will cause further swelling and increase the risk of infection. Most tick bites will heal within three weeks.
Seek medical attention if you've been unable to remove all of the tick. You should also see your GP if you develop:
- a pink or red rash
- a temperature of 38°C (100.4°F) or above
- other flu-like symptoms, such as a headache or joint pain
- swollen lymph nodes
You may need antibiotics to prevent Lyme disease.
Read more about how Lyme disease is treated.
A number of complications can develop after you are bitten or stung by an insect, including secondary infection, Lyme disease, West Nile virus and malaria.
A number of complications can develop after being bitten or stung by an insect.
Secondary bacterial infections are a common complication of insect bites and stings. They include:
- impetigo – a highly contagious bacterial infection that causes sores or blisters
- cellulitis – an infection that makes your skin red, swollen and painful
- folliculitis – inflammation of one or more hair follicles (the small holes in your skin that hair grows out of)
- lymphangitis – an infection that causes red streaks in your armpit or groin and swollen lymph nodes (small glands that are part of the immune system)
An infection can occur if you scratch an insect bite or sting, or it may be introduced at the time you're bitten.
Infections are usually treated with antibiotics.
Lyme disease is an infection caused by a species of tick known as Ixodes ricinus. Ticks aren't insects – they're small arachnids.
There are an estimated 2,000-3,000 cases of Lyme disease in England and Wales each year, with about 15 to 20% of cases occurring while people are abroad.
Your risk of developing Lyme disease is increased if you spend a lot of time in woodland or heath areas as these areas are where tick-carrying animals, such as deer and mice, live.
The initial infection is characterised by a red rash that gradually expands outwards from the site of the bite. Antibiotics are usually used to treat the infection.
If untreated, the long-term effects of Lyme disease include problems with the nervous system, such as:
- meningitis – an infection of the protective membranes that surround the brain and spinal cord
- facial palsy – weakness of the facial muscles that causes drooping of one or both sides of the face
- encephalitis – an uncommon but serious condition that causes inflammation of the brain
The condition can also damage the joints, which can lead to arthritis and, occasionally, heart problems, such as inflammation of the heart muscle (myocarditis) and inflammation of the fluid-filled sac that surrounds the heart (pericarditis).
West Nile virus
There have been no reported cases of West Nile virus in the UK, but there have been cases elsewhere in the world.
Malaria is a tropical disease caused by an infection of the red blood cells. It can be transmitted to humans by the bite of an infected mosquito.
Each year, there are around 1,500 cases of malaria in travellers returning to the UK. A certain type of malaria caused by the parasite Plasmodium falciparum is potentially fatal. It accounts for more than half of all cases of malaria in the UK each year.