Content Supplied by NHS Choices

Bites-insect

Insect bites and stings are puncture wounds caused by insects. Some insects may sting you as a defence by injecting venom into your skin.

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.

Read more about the symptoms of insect bites and stings.

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

Read more about the complications of an insect bite or sting.

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 or ibuprofen.

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

Read more about treating insect bites and stings.

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.

Read more about preventing insect bites and stings.

Travelling abroad

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

  • Africa
  • Asia
  • 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.

Read more about travel illnesses and vaccinations.

Content Supplied by NHS Choices

Bites-insect

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. 

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.

Fleas

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.

Horseflies

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)
  • dizziness
  • weakness
  • wheezing
  • 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.

Bedbugs

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:

  • face
  • neck
  • hands
  • arms

Read more about bedbugs.

The Blandford fly

The Blandford fly (sometimes called blackfly) is usually found near rivers. It's common in:

  • Dorset
  • East Anglia
  • Oxfordshire
  • Herefordshire

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:

  • swelling
  • blistering
  • a high temperature of 38C (100.4F) or over
  • joint pain

Arachnid bites

Ticks

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:

  • swelling
  • itchiness
  • blistering
  • bruising

Ticks can carry a bacterial infection called Borrelia burgdorferi, which causes Lyme disease. Lyme disease can be serious if it isn't treated.

Mites

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.

Spiders

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.

Bees

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 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
  • nausea
  • 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.

Content Supplied by NHS Choices

Bites-insect

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.

Infection

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 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

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

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.

Share this page