Bites, insect

Insect bites are puncture wounds caused by insects. In Ireland, insects that bite include:

  • midges
  • mosquitoes
  • fleas
  • bedbugs
  • ticks

When an insect bites, it releases saliva that can cause:

  • inflammation (redness and swelling)
  • blisters
  • irritation

The symptoms of insect bites can vary depending on the type of insect and the sensitivity of the person who is bitten. For example, some people may have a small, itchy lump after they are bitten, which only lasts for a few hours. Others may develop a more serious reaction, such as blistering and a number of itchy, red lumps. See Insect Bites Symptoms for more information.

Bite or sting?

As well as insects that bite, some insects sting and inject venom into the wound. In Ireland, insects that sting include:

  • bees (honeybees and bumblebees)
  • wasps

See the Health A-Z topic about Insect stings for more information, including how to treat them.

Risk factors

If you work outdoors or regularly take part in outdoor activities, such as camping or hiking, you are more likely to be bitten by an insect. Exposing large areas of skin, such as your legs and arms, leaves you open to being bitten.

When should I see a doctor?

See your GP if your symptoms are severe (for example, if you have a lot of swelling and blistering) or if there is pus, which indicates an infection.

If you have a severe allergic reaction to a bite, such as wheezing or difficulty breathing, call 999 or 112.

If you have 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. See Insect bites - treatment for advice on how to do this.

Outlook

Most insect bites get better within a few hours. Tick bites usually take about three weeks to heal, although they can last for months if part of the tick is left in the wound.

Some insect bites can cause severe reactions, but it is unusual to catch diseases after being bitten by an insect in Ireland. The risk of catching diseases, such as malaria (a serious and sometimes fatal condition that causes a high temperature) is much greater in countries such as:

  • Africa
  • Asia
  • South America

Inflammation

Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Flea bites can be grouped in lines or clusters and can cause a number of itchy red lumps to form 

Treating insect bites

Most insect bites cause itching and swelling that usually clears up within a few hours. You can treat minor bites by:

  • washing the bite with soap and water
  • placing a cold compress (a flannel or cloth soaked in cold water) over the affected area to reduce swelling
  • not scratching the bite

If you are in pain or the bite is swollen, you can take painkillers, such as paracetamol or ibuprofen . See Insect bites - treatment for more information and advice.

An insect bite often causes a small lump to develop, which is usually very itchy. A small hole (the actual bite) 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 usually clear up within several hours and they can be safely treated at home. 

Allergic reactions

Some people are particularly sensitive to certain insect bites and can react badly to them if they are bitten.

If you are very sensitive to an insect bite, you may experience anaphylaxis (also known as anaphylactic shock). This is when your immune system (the body's defence system) reacts badly to the insect bite. However, anaphylaxis after an insect bite is rare. You are more likely to have an allergic reaction if you are stung by an insect.

See the Health A-Z topics about Anaphylaxis and Insect stings for more information.

It is important to know the symptoms of a severe allergic reaction. If you or someone you know is bitten or stung by an insect and experiences a severe reaction, emergency medical treatment will be required.

Symptoms of a severe allergic reaction may include:

  • wheezing or difficulty breathing
  • severe itching or a blotchy rash over many parts of your body
  • severe swelling that may be visible in your lips or tongue
  • dizziness
  • nausea (feeling sick)
  • chest pain

Call 999 or 112 for an ambulance if you or someone you know has these symptoms after being bitten or stung by an insect.

Types of insect bite

The symptoms that can occur from different types of insect bites are listed 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 are 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 (a condition that causes a high temperature and can be fatal). See the Health A-Z topic about Malaria for more information about this condition.

Fleas

Flea bites can be grouped in lines or clusters. If you are 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. They may also affect the forearms if you have 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 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 are not usually painful, and if you have 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

Ticks

Tick bites are not 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 (a bacterial infection that causes a rash and high temperature). If Lyme disease is not treated, its effects can be serious (see Insect bites - complications ).

See the Health A-Z topic about Lyme disease for more information about this condition.

Mites

Mites cause very itchy lumps to appear on the skin and can also cause blisters. If the mites are from pets, you may be bitten on your abdomen (tummy) and thighs where the pet has been sitting on your lap. Otherwise, mites will bite any uncovered skin.

Allergic
An allergen is a substance that reacts with the body's immune system and causes an allergic reaction.
Antibiotic
Antibiotics are medicines that can be used to treat infections caused by micro-organisms, usually bacteria or fungi. Examples of antibiotics include amoxicillin, streptomycin and erythromycin.
Inflammation
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.

Infected bites

Sometimes, insect bites can become infected. Symptoms of an infected insect bite may include:

  • pus in or around the bite
  • swollen glands
  • increasing redness, swelling and pain in and around the bite

Some bites will naturally be red and swollen, but for other types of bites these symptoms may not be normal and could indicate an infection.

If you think your bite may have become infected, or if you are concerned about your symptoms, see your GP.

Sensitisation

If an insect bites you, you may become 'sensitive' to its saliva. This means that if you are bitten again by the same or a similar species, it can provoke a local reaction. A local reaction is a reaction that is confined to the area of the bite.

For example, you may develop:

  • an itchy papule (lump)
  • an itchy weal (an inflamed, fluid-filled area)

This may last for several days.

The severity of the reaction will depend on your level of sensitivity. However, if you continue to be exposed to the insect's saliva (you continue to be bitten), you will eventually become immune to the saliva and there will be no reaction at all.

Insects in Ireland that may bite include:

  • midges (small flying insects)
  • gnats (small flying insects)
  • mosquitoes 
  • flies
  • fleas, which usually live on an animal or person
  • bedbugs, which live inside mattresses or furnishings, or behind skirting boards or paintings (they cannot fly)
  • ticks, which live in areas with long grass, moorland and in forests where deer are found, and are about the size of a poppy seed
  • mites, which are found in stored products, such as flour or grain, or on cats and dogs

Risk factors

Some risk factors that can make insect bites more likely are discussed below.

  • Pets, such as dogs and cats, are a common cause of persistent flea bites. You may have pets of your own, or you may be bitten if you frequently visit someone who has pets.
  • Living environment. Infestations of human fleas often occur in overcrowded communities that have low hygiene standards.
  • Birds nesting on or near the house. Household infestations of bird fleas can occur if bird boxes are positioned too close to your house. 
  • Recent house move. If you have recently moved house and you have bites, they may be caused by fleas. Fleas can survive for a few months without a host (an animal or person that fleas live on in order to survive).
  • Old houses, furniture and upholstery can contain bedbugs, which can travel a considerable distance to find a suitable host.
  • Occupation. People who work outdoors, such as forestry workers, are at increased risk of being bitten by ticks or midges. People who handle products, such as dockworkers, warehouse workers or shopkeepers, are most at risk of being bitten by mites. 
  • Travel. Bites may be caused by a foreign insect, such as a botfly, which is found in certain parts of South America.
  • Pregnancy. Mosquitoes are attracted to pregnant women, possibly because they produce more carbon dioxide and give off more heat, which mosquitoes find attractive. 
  • Ulcers. If you have ulcers (open sores) on your skin, this may attract flies, as they like to lay their eggs in rotting flesh.


 

An insect bite is usually obvious from the symptoms. Tell your GP if you know that you were exposed to a particular type of insect.

Your GP may look for the following symptoms in order to confirm your diagnosis.

Irritation

Irritation is usually a constant symptom. Avoid rubbing or scratching the affected area because it can make the irritation worse and may lead to infection.

Papular urticaria

Papular urticaria is a number of very itchy red lumps (papules) that develop on or near the area of the bite. They can also develop fluid-filled blisters that may crust over if scratched. Papules can persist for up to two weeks.

Papular urticaria is particularly common in children. It usually affects children who:

  • are two to seven years of age
  • have a history of atopic dermatitis, a condition that causes inflammation of the skin and often runs in families

Papular urticaria is caused by being very sensitive to insect bites.

Bullous reaction

Bullous reactions are where fluid-filled blisters develop on your skin. They are particularly common in children and often occur on the lower legs.

Fever

A fever (high temperature) may occur if there are numerous bites, or if there is a severe local reaction. A fever is usually 38C (100.4F) or over.

Most insect bites cause small, local reactions (reactions that are confined to the area of the bite) where the symptoms can be easily treated. However, if your symptoms are severe, see your GP as soon as possible.

If you have a severe allergic reaction to an insect bite, such as wheezing or difficulty breathing, call 999 or 112 immediately to request an ambulance.

Small, local reactions

Most insect bites cause itching and swelling that usually clear up within several hours. If you were bitten by a tick, you need to remove it (see box, right).

Small, local reactions can be treated by:

  • washing the bite 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 bite because this can make the bite more itchy and swollen and increase the chance of a secondary infection (see Insect bites - complications)

Medication

If you are in pain or the bite is swollen, you can take painkillers, such as paracetamol or ibuprofen. These are available over the counter without a prescription. Always read the manufacturer's instructions to make sure they are suitable for you and that you are taking the correct dose.

If the bite is very itchy, your GP may prescribe crotamiton cream. This should be applied two or three times a day, or just once a day for children under three years of age. Alternatively, a corticosteroid cream can be used to soothe the pain of a bite.

See the Health A-Z topic about Topical corticosteroids for more information about this type of medicine.

Do not apply cream or ointment to broken skin and always follow the instructions on the packet. Although the bite may be itchy, avoid scratching it because you may damage the skin and allow bacteria to enter the wound, leading to an infection.

If itching is disturbing your sleep at night, your GP may prescribe you a type of antihistamine tablet that makes you feel drowsy, to help you sleep. Antihistamine medicine is usually used to treat allergic reactions.

See the Health A-Z topic about Antihistamines for more information about this type of medicine. 

Large, local reactions

Large, local reactions are reactions that occur beyond the site of the bite, for example causing a large area to swell or causing severe pain.

Medication

Painkillers, such as paracetamol or ibuprofen, can be taken to relieve the pain. These are available over-the-counter (OTC) without a prescription. Always read the manufacturer's instructions to make sure they are suitable for you and that you are taking the correct dose.

You may also be prescribed a short course of antihistamines. These are taken orally (by mouth). You can take non-sedating antihistamines during the day and sedating antihistamines at night if the itching is affecting your sleep.

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.

 

Blisters

If you develop blisters (small pockets of fluid) after being bitten by an insect, do not burst them because they may become infected. Blisters do not often cause pain unless they rupture (burst), exposing the new skin underneath. If possible, use an adhesive bandage (plaster) to protect the blistered area.

See the Health A-Z topic about Blisters for more information.

Infected bites

See your GP if your bite becomes infected (see Insect bites - symptoms for the signs of an infected bite). Your GP may prescribe oral antibiotics (medicines to treat infections that are caused by bacteria). You will need to take these as instructed, usually two or four times a day for seven days. 

Allergy clinics

If previous insect bites have caused a large skin reaction, such as redness and swelling of over 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 is available in your local area.

Immunotherapy (desensitisation or hyposensitisation) is a possible treatment option if you are allergic to insect bites.

Immunotherapy works by gradually introducing more and more of the substance that you are allergic to, in this case the saliva of a particular insect, into your body. This makes you less sensitive to the substance and eventually your body stops reacting to it. Immunotherapy is more commonly used for wasp or bee stings.

See the Health A-Z page about treating allergies for more information about immunotherapy.

Infestation

If you are bitten by fleas, mites or bedbugs, you may have an infestation (a large amount of the insects) in your home. Try to find the source of the infestation and then take 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.

If you are unsure whether your pet has fleas, speak to your veterinary surgeon (vet).

Eliminating an infestation

Once you have identified the cause of the infestation, you will 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, 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.

Ticks

If you have 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 rash). See Insect bites - complications for more information about this condition.
 
To remove the tick:

  • Use tweezers, wear gloves or cover your fingers with tissue to avoid touching the tick.
  • Grab the tick as close to the skin as you can, and gently pull straight up until all parts are removed.
  • Do not twist or jerk the tick as you are removing it because this may cause the mouthparts to break off and remain in your skin once the tick has been removed.
  • Wash your hands with soap and water.
  • Using petroleum jelly, alcohol or a lit match to remove a tick does not work.

After the tick has been removed, clean the tick bite with soap and water or an antiseptic (a substance that reduces the growth and development of germs), such as an iodine scrub.

Do not scratch the bite because this will cause further swelling and increase the chance of infection. Most tick bites will heal within three weeks. See your GP if you develop:

  • a rash
  • a fever (high temperature) of 38C (100.4F) or over

You may need antibiotics to prevent Lyme disease. See the Health A-Z topic about Lyme disease for more information about this condition, including the symptoms and treatment.

A number of complications can develop after you are bitten by an insect.

Secondary bacterial infection

Secondary bacterial infections are a common complication of insect bites. 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 (redness and swelling) of one or more hair follicles (the small hole in your skin that an individual 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 may occur if you scratch an insect bite, or it may be introduced at the time you are bitten.

Infections are usually treated with antibiotics (medication to treat infections that are caused by bacteria), such as flucloxacillin. If you are allergic to penicillin, alternatives include erythromycin or clarithromycin. These will usually be taken orally (by mouth) two or four times a day for seven days.

Lyme disease

Lyme disease is an infection that is caused by the bacterium Borrelia burgdorferi, and is transmitted by a species of tick known as Ixodes ricinus.

Lyme disease is uncommon in Ireland, but the Health Protection Surveillance Centre estimates that there are between 50 to 100 cases of Lyme disease in Ireland every year. 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 (brain, spinal cord and nerves) such as:

  • meningitis: an infection of the meninges (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 inflammation (swelling) of the brain (this is rare)

The condition can also damage the joints which can lead to:

arthritis pain and inflammation of the joints and bones

  • heart problems (occasionally), such as inflammation of the heart muscle (myocarditis) and inflammation of the thin, two-layered, sac-like tissue that surrounds the heart (pericarditis)

See the Health A-Z topic about Lyme disease for more information about this condition.

West Nile virus

West Nile virus is an infection with flu-like symptoms that can be passed on to humans by mosquitoes. Mosquitoes become infected when they feed on infected birds.

There have been no reported cases of the West Nile virus in tIreland, but there have been cases elsewhere in the world.

See the Health A-Z topic about West Nile virus for more information about this condition.

Malaria

Malaria is a tropical disease that is caused by an infection of the red blood cells (the cells that carry oxygen in the blood). It can be transmitted to humans by the bite of an infected mosquito.

Each year, there are around 100 cases of malaria in travellers returning to Ireland. A certain type of malaria, known as Plasmodium falciparum, is potentially fatal and accounts for over half of all annual cases.

See the Health A-Z topic about malaria for more information about this condition.

There are a number of precautions that you can take to avoid being bitten by insects. It is particularly important to follow this advice if you have had a bad reaction to an insect bite in the past.

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

  • Cover exposed skin. If you are 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. This should be applied to exposed areas of skin. Repellents that contain diethyltoluamide (DEET) are considered to be the most effective.
  • Avoid using products with strong perfumes. Do not use strong-smelling products, such as soaps, shampoos and deodorants, because they can attract insects.
  • Avoid flowering plants, outdoor areas where food is served, rubbish and compost areas.
  • Remove and destroy insect nests. If a nest is in or near your house, arrange to have it removed.
  • Avoid flea infestations. If you have pets, they should be regularly treated for fleas.
  • Avoid camping near water, such as ponds and swamps, because mosquitoes and horseflies are commonly found near water.

Avoiding ticks

Avoid tick-infested areas where possible. Local health departments and parks should be able to give you information about tick-infested areas. If you cannot avoid a tick-infested area, walk in the centre of paths to avoid contact with vegetation.

Travelling

Seek medical advice before travelling to a tropical area where there is a risk of catching malaria (a condition that causes a high temperature and can be fatal). You may need to take antimalarial tablets to avoid becoming infected. See the Health A-Z page about preventing malaria for more information.

When you reach your destination, make sure that 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 stop you being bitten.

Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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