The cause of an insect bite may be the result of a number of things. Some of the factors which can cause insect bites are listed below.

• Pets - pets, such as dogs and cats, are a common cause of persistent fleabites. You may not have pets of your own, but you may be bitten if you frequently visit someone who has pets.
• Living environment - infestations of human fleas often occur in overcrowded communities with low standards of hygiene.
• 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 (even one that has been empty for some time), and you have bites, it may be because of fleas. Fleas can survive for a few months without a host (an animal, or person, which fleas live on and need to survive).
• Old houses, furniture, and upholstery - can contain bedbugs, which can travel a considerable distance to find a suitable host.
• Occupation - those who work outdoors, such as forestry workers, have an increased risk of being bitten by ticks. People who handle products, such as dockworkers, warehouse workers, or shopkeepers, are most at risk of getting mite dermatitis (a condition where contact with mites causes irritation to the skin).
• Travel - bites may be caused by a foreign insect, such as a botfly, which is found in certain parts of south America.

There are a number of complications that can develop after being bitten by an insect.

Secondary bacterial infection

Secondary bacterial infections, such as impetigo, cellulitis, or lymphangitis, are common complications of insect bites. An infection may occur if you scratch an insect bite, or may be introduced at the time you are bitten.

Staphylococcal and streptococcal skin infections are usually treated with antibiotics, such as oral flucloxacillin. If you are allergic to penicillin, oral erythromycin or clarithromycin, may be used as alternatives.

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 the UK, but the number of cases is rising with an average of 595 cases annually, 82% of which are acquired in the UK. 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 nervous system problems, such as:

• meningitis,
• facial palsy (weakness of the facial muscles causing drooping of one or both sides of the face),
• radiculopathy (causing a shingles-type pain, usually on the trunk of the body, or a limb), and
• in rare cases, encephalitis (inflammation of the brain).

The condition can also cause damage to the joints which can lead to arthritis and, occasionally, heart problems, such as inflammation of the heart muscle (myocarditis) and inflammation of the thin, two-layered, sac-like tissue that surrounds the heart (pericarditis).

West Nile virus

West Nile virus is an infection with flu-like symptoms that can be passed on to humans by a certain species of mosquito, known as Culex spp. This type of mosquito is present in the UK, but not in significant enough numbers to pose a substantial risk.

Although there have been no reported cases of West Nile virus in the UK, there have been cases elsewhere in the world, and since 2001, the Health Protection Agency (HPA) and the Department of Health have been raising awareness of the infection among the UK healthcare community.

Malaria

Malaria is a tropical disease that is caused by an infection of the red blood cells. It can be transmitted to humans by the Anopheles mosquito. Each year, over 2,000 cases are imported into the UK. A certain type of malaria (known as P falciparum) is potentially fatal and accounts for over half of all annual cases in the UK.

The diagnosis of insect bites is usually obvious from the symptoms, and on the basis of known exposure to particular insects. However, your GP may use the following to confirm a diagnosis.

• Irritation is usually a constant symptom. You should avoid rubbing, or scratching, the affected area because doing so can make the irritation worse, and may lead to infection.
  
• Papular urticaria is a condition that is particularly common in children who are between 2-7 years of ages, and it is caused by a hypersensitivity to the bites of fleas, lice, bedbugs, gnats, mites, and other insects. Papular urticaria causes lesions, or papules (small, raised lumps) to develop on, or near, the area of the bite. Papules are usually very itchy and can persist for up to two weeks.
  
• Bullous reaction is where fluid-filled blisters develop on your skin. They are particularly common in children, and often occur on the lower legs.
  
• Fever may occur if there are numerous bites, or if there is a severe local reaction.

Insect bites are puncture wounds, or lacerations, caused by insects. In the UK, insects that bite include:

• Midges.
• Gnats.
• Mosquitoes.
• Flies.
• Fleas.
• Bedbugs.

When an insect bites, it releases a form of saliva that can cause symptoms such as inflammation, blisters, and irritation.

Symptoms vary according to the type of insect involved, and the sensitivity of the person bitten. For example, a bite may result in a small, itchy lump that lasts for just a few days, or it can lead to a more serious reaction, such as papular urticaria (see the 'Diagnosis' section).

You are more likely to be bitten by an insect if you work outdoors or regularly take part in outdoor activities such as camping or hiking. If large areas of your skin are exposed, such as on your arms or legs, these areas are more are more vulnerable to being bitten by an insect.

Although some insect bites can cause severe reactions, it is unusual to catch diseases from them in the UK. However, in certain countries in Africa, Asia, and South America, the risk of catching diseases such as malaria is much greater.

There are a number of precautions you can take to prevent 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 the day when insects are particularly active, such as at dawn or dusk, 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 DEET (diethyltoluamide) are considered to be the most effective.
  
• Avoid using products with strong perfumes - you should avoid using strong smelling products, such as soaps, shampoos and deodorants, as these 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 (your local council, or a pest control expert should be able to remove the nest for you).
  

Avoiding ticks

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

Camping

If you are camping, avoid campsites near water, such as ponds and swamps, where mosquitoes and horseflies are commonly found. To avoid flea infestations in the home, get your pets regularly treated. To avoid bedbugs, wash bedding regularly at a high temperature and regularly replace old mattresses and pillows.

Travelling

Before travelling to a tropical area, where there is a risk of catching malaria, you should seek medical advice. 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 to prevent you being bitten.

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 area around it that may be filled with fluid. This is called a weal.

Insect bites usually clear up within several days and can be safely treated at home.

Allergic reactions

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

However, severe allergic reactions to insect bites are rare. You are more likely to have an allergic reaction if you are stung by an insect. Never the less, it is still important to be aware of the symptoms of a severe allergic reaction, as it will require emergency treatment.

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 which may be visible in your lips or tongue,
• dizziness,
• nausea, or
• chest pain.
  

Call 999 for immediate emergency medical assistance if, following an insect bite, or sting, you, or someone you know, is displaying these symptoms.

Symptoms of an infected bite

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

• pus in, or around, the bite,
• swollen glands, or
• flu-like symptoms.

Another sign of an infected insect bite can be increasing redness, swelling, and pain in, and around, the bite. Some bites will naturally be red and swollen, but for other types of bite, these symptoms may be abnormal.

If you suspect that your bite may have become infected, or you are concerned in any way about your symptoms, you should see your GP, or call NHS Direct on 0845 46 47.

Sensitisation

If you are bitten by an insect, you may become 'sensitive' to its saliva. Being bitten again by the same, or a similar species, can provoke a local reaction to occur. For example, an itchy papule (lump), or an itchy weal (an inflamed, fluid-filled area) may develop, and 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.

Prognosis

Most insect bite reactions only last for a few hours and clear up quickly. However, occasionally, they can persist for several months. If you have a persistent infection following an insect bite, you may need to have follow-up treatment. You should seek advice from your GP about this.

In the case of tick bites, persistent reactions can occur, particularly if some of the insect's mouth parts are not removed from your skin. However, most tick bites heal within three weeks.

The symptoms that can occur from different types of insect bite 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, bullae (blisters) or weals (circular, fluid-filled areas surrounding the bite) may develop.

Mosquito bites in certain areas of tropical countries can cause malaria.

Fleas

Fleabites can be grouped in lines, or clusters. If you are particularly sensitive to flea bites, they can lead to a condition known as papular urticaria (where lumps, or lesions, form). Bullae (fluid-filled blisters) may also sometimes develop. Cat and dog fleabites often occur below the knee, commonly around the ankles.

Horseflies

A bite from a horsefly can be very painful, and as well as the formation of a weal around the bite, you may experience:

• urticaria (a rash of weals),
• dizziness,
• weakness,
• wheezing, or
• angio-oedema (itchy, pale pink, or red, swellings that often occur around the eyes and lips for short periods of time).

As horseflies cut the skin when they bite (rather than pierce it), horsefly bites can take a long time to heal, and they can cause infection.

Bedbugs

Bites from bedbugs are not usually painful, and if you have not been bitten previously, you may not have any symptoms. However, if you are sensitised, you may develop intensely irritating weals (inflamed, fluid-filled area) or papules (lumps). Bites often occur on your face, neck, hands, and arms.

The Blandford fly

The Blandford fly (sometimes called blackfly) is found in east Anglia, Oxfordshire and Dorset.

Blandford fly bites are common during May and June, and are very painful, frequently occurring on the legs. They can produce a severe, localised reaction, with symptoms including oedema (itchy, pale pink, or red, swellings), blistering, fever, and joint pain.

Ticks

Ticks live in long grassy areas, and in forests where deer are found. Tick bites are not usually painful, and sometimes only cause a red papule (lump) to develop at the bite site.

However, ticks can carry a bacterial infection, called Borrelia burgdorferi, which causes Lyme disease. If Lyme disease is not treated, its effects can be serious (see the 'complications' section).

Most insect bites result in small, local reactions where the symptoms can be easily treated. However, if your symptoms are severe, you should visit your GP as soon as possible.

If you have a severe allergic reaction to an insect bite, such as wheezing, or other signs of respiratory distress, you should call 999 immediately for medical assistance.

Small, local reactions

The majority of insect bites cause itching and swelling which usually clears up within several days. Small, local reactions (reactions confined to the area of the bite) can be treated using a cold compress (such as placing a damp flannel over the affected area), and oral painkillers, such as paracetamol or ibuprofen.

Anaesthetic, or steroid cream, such as crotamiton cream, can be used to soothe the pain of a bite. Antihistamine tablets can also help.

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 get in, leading to infection.

Large, local reactions

Large, local reactions can be treated using a short course of an oral antihistamine and oral analgesics. If local swelling is severe, your GP may prescribe a short course of oral steroids.

Generalised urticaria

If after being bitten by an insect, you, or a family member, show signs of urticaria (small, itchy lumps or lesions on or near the bite site) your GP may prescribe an oral antihistamine and an oral corticosteroid, such as prednisolone. If the symptoms worsen, you should seek medical assistance immediately.

Blisters

If you develop blisters after being bitten by an insect, do not burst them as they may become infected. Blisters do not often cause pain unless they rupture, exposing tender skin underneath. If possible, use an adhesive bandage to protect the blistered area.

Allergy clinics

If previous insect bites have caused generalised symptoms other than at the bite site, such as a large skin reaction, with redness and swelling of over 10cms in diameter, your GP may refer you to see a specialist at an allergy clinic. Immunotherapy (desensitisation) is a possible treatment option if you are allergic to insect bites or stings.

Below is some advice relating to specific types of insect bite.

Midges, mosquitoes, and gnats

Most midge, mosquito, or gnat bites do not require treatment and will clear up within 1-2 days. In cases where there is no allergic reaction, a cold compress, such as a cold flannel or ice pack, can be used to ease any pain and inflammation.

Steroid creams, such as hydrocortisone, or antihistamines (cream or tablets) are available over-the-counter at pharmacies, as well as on prescription, and will help to ease any itchiness and inflammation.

If you have severe symptoms, such as swelling and blistering, you should continue to use the above treatment methods, and visit you GP as soon as possible. You may require further treatment, such as a course of steroids.

Fleas, mites, or bedbugs

If bitten by fleas, mites, or bedbugs, you may have an infestation in your home. You should try to find the source of the infestation - for example, a dog or a cat. Once you have identified the cause of the infestation.

If your pet is the source of the flea infestation, you will need to treat it, its bedding, household carpets and soft furnishings with an insecticide. Thoroughly vacuum your carpets and soft furnishings.

In the case of a Cheyletiella mite infestation, you should seek advice from your local veterinary surgeon, as aggressive treatment is required.

If an infestation of bedbugs is confirmed, your home will need to be thoroughly treated with insecticide by a reputable pest control company (contact your local council for details).

You will need to vacuum carpets and upholstery, and wash bed linen and clothing using the hottest possible wash. Children and pets should be removed from the property during the treatment which should take a few hours to complete. Further treatments may be necessary to get rid of the bugs.

Ticks

If bitten by a tick, you should remove it as soon as possible to reduce the risk of getting a tick borne infection, such as Lyme disease (see complications section).

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, as this may cause the mouthparts to break off and remain in your skin. Using petroleum jelly, alcohol, or a lit match to remove a tick does not work.

Once the tick has been removed, wash your hands with soap and water. Clean the tick bite with soap and water,  apply ice to reduce any swelling and use an antiseptic.

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 around your armpit, groin and thighs, or get a flu-like illness after being bitten by a tick. You may need antibiotics to prevent Lyme's disease.

Blandford fly

See your GP if you notice red lines appearing on your skin, or enlarged lymph nodes (swelling) in your armpit or groin. These symptoms can be casued by the Blandford fly.