False widow (spider) bite


False widow (spider) bite


Insect bites and stings are common and usually only cause minor irritation. However, some stings can be painful and trigger a serious allergic reaction.

In the UK, insects that bite include midges, mosquitoes, fleas, bedbugs and, although not strictly insects, spiders, mites and ticks, which are arachnids. Insects that sting include bees, wasps and hornets.

An insect bites you by making a hole in your skin to feed. Most insects sting as a defence by injecting venom into your skin.

Symptoms of an insect bite or sting

When an insect bites, it releases saliva that can cause the skin around the bite to become red, swollen and itchy.

The venom from a sting often also causes a swollen, itchy, red mark (a weal) to form on the skin. This can be painful, but it's harmless in most cases. The affected area will usually remain painful and itchy for a few days.

The severity of bites and stings varies depending on the type of insect involved and the sensitivity of the person.

In rare cases, some people can have a serious allergic reaction(anaphylaxis) to a bite or sting that requires immediate medical treatment.


When to seek medical help

See your GP if you've been bitten or stung and there's a lot of swelling and blistering or if there's pus, which indicates an infection.

Dial 999 and ask for an ambulance if you experience any of these symptoms after a bite or sting:

wheezing or difficulty breathing

nausea, vomiting or diarrhoea

a fast heart rate

dizziness or feeling faint

difficulty swallowing (dysphagia)

confusion, anxiety or agitation


Treating insect bites and stings

Most bites and stings are treated by:

washing the affected area with soap and water

placing a cold compress (a flannel or cloth soaked in cold water) over the area to reduce swelling

Try not to scratch the affected area to avoid infection. If you're in pain or the area is swollen, take painkillers such as paracetamol oribuprofen.

If you have a more serious reaction, your GP may prescribe other medication or refer you to an allergy clinic for immunotherapy (desensitisation).


Preventing insect bites and stings

You're more likely to be bitten or stung if you work outdoors or regularly take part in outdoor activities, such as camping or hiking.

Using insect repellent and keeping your skin covered when outdoors will help you avoid being bitten or stung.

Try not to panic if you encounter wasps, hornets or bees, and back away slowly. Don't wave your arms around or swat at them.


Travelling abroad

There's a risk of catching diseases such as malaria from insect bites in certain parts of the world, such as:



South America

It's therefore important to be aware of any risks before travelling to these areas, and to get any necessary medication or vaccinations.

Symptoms of insect bites and stings 

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. 

Insect bites

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:






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

Arachnid bites



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.

Insect stings


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.

Allergic reaction

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 requireallergy 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.

Treating insect bites and stings 

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.

Basic treatment

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.  

Additional treatment

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, antihistamineor 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.

Infected bites

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.

Allergic reaction

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.

Allergy clinics

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.



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

Complications of insect bites and stings 

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

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 toarthritis 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

West Nile virus is an infection with flu-like symptoms that is spread by mosquitoes. 

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.

Preventing insect bites and stings 

There are a number of precautions you can take to avoid being bitten or stung by insects.

It's particularly important to follow this advice if you've had a bad reaction to an insect bite or sting in the past.

Some of the precautions you can take to minimise your risk of being bitten or stung by an insect are listed below.

move away slowly and don't panic if you encounter wasps, hornets or bees – don't wave your arms around or swat at them

cover exposed skin – if you're outside at a time of day when insects are particularly active, such as sunrise or sunset, cover your skin by wearing long sleeves and trousers

wear shoes when outdoors

apply insect repellent to exposed areas of skin, particularly in summer or early autumn, when stings are most likely to occur – repellents that contain diethyltoluamide (DEET) are most effective

avoid using products with strong perfumes, such as soaps, shampoos and deodorants – they can attract insects

avoid flowering plants, outdoor areas where food is served, rubbish and compost – regularly and carefully remove any fallen fruit in your garden and keep a well-fitting lid on dustbins

never disturb insect nests – wasps build nests in sheltered areas such as trees and roof spaces; if a nest is in or near your house, arrange to have it removed (see the GOV.UK website for details about pest control services and how your local council can help) 

avoid camping near water, such as ponds and swamps – mosquitoes and horseflies are commonly found near water

keep food and drink covered when eating or drinking outside, particularly sweet things – wasps or bees can also get into open drink bottles or cans you're drinking from

keep doors and windows closed or put thin netting or door beads over them to prevent insects getting inside the house – also keep the windows of your car closed to stop insects getting inside


Avoiding ticks

Ticks are small arachnids that are mainly found in woodland areas. They attach to your skin, suck your blood and can cause Lyme disease.

The best ways to avoid ticks include:

being aware of ticks and the type of habitats where ticks usually live

wearing appropriate clothing in tick-infested areas (a long-sleeve shirt and trousers tucked into your socks)

wearing light-coloured fabrics to help you spot a tick on your clothes

using insect repellents

inspecting your skin for ticks, particularly at the end of the day, including your head, neck and skin folds (armpits, groin, and waistband)

checking your children's head and neck areas, including their scalp

making sure ticks aren't brought home on your clothes

checking that pets don't bring ticks indoors on their fur



If you're bitten by fleas, mites or bedbugs, you may have an infestation in your home. Try to find the source of the infestation before taking steps to eliminate it.

Signs of an infestation

The following are signs of an infestation:

fleas or flea faeces (stools) in your animal's fur or bedding are a sign of fleas

crusting on your dog's fur is a sign of fleas

excessive scratching and grooming are a sign of fleas in your cat

dandruff (flakes of skin) on your cat or dog is a sign of mites

spots of blood on your bed sheets are a sign of bedbugs

an unpleasant almond smell is a sign of bedbugs

Speak to your veterinary surgeon if you're unsure whether your pet has fleas.

Eliminating an infestation

Once you've identified the cause of the infestation, you'll need to eliminate it.

For flea infestations, treat the animal, its bedding, household carpets and soft furnishings with an insecticide. Thoroughly vacuum your carpets and soft furnishings.

For mite infestations, you should seek advice from your vet as aggressive treatment is required.

For bedbug infestations, your home will need to be thoroughly treated with an insecticide by a reputable pest control company. See the GOV.UK website for details of pest control services and more information about how your local council can help with an infestation.


Travelling abroad

Seek medical advice before travelling to a tropical area where there's a risk of catching malaria. You may need to take antimalarial tablets to avoid becoming infected.

When you reach your destination, make sure your accommodation has insect-proof screen doors and windows that close properly.

Sleeping under a mosquito net and spraying rooms with insecticide will also help prevent you being bitten.