Bites

Insect bites are puncture wounds, or lacerations, caused by insects. In the UK, insects that bite include midges, gnats, mosquitoes, flies, fleas, and bedbugs.

When an insect bites, it releases a form of saliva that can lead to symptoms, such as inflammation, blisters, and irritation. Symptoms can vary depending on the type of insect involved, and the sensitivity of the person who is 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 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 vulnerable to being bitten by an insect.

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

The cause of an insect bite may be the result of a number of things. For example, it may be due to:

- Pets, such as dogs and cats, are a common cause of persistent fleabites. If you do not have pets of your own, you may be bitten if you frequently visit someone who does have 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, and they 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, and 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 can be found in certain parts of South America.

Some people are particularly sensitive to certain insect bites and stings and, when they are bitten, react badly to them. Allergic reactions, such as blistering, or severe rashes, can be very serious and, in extreme cases, may even be life threatening. In such cases, you should dial 999 for emergency assistance.

An insect bite often causes a small lump to develop which is usually very itchy. A small hole (the actual bite) may be visible. The lump may have an inflamed area around it that may be filled with fluid. This is called a weal.

Insect bites normally clear up within 1-2 days.

However, if, after being bitten by an insect, any of the following symptoms occur, you should see your GP as soon as possible because the bite might be infected:

- it becomes swollen,
- it does not disappear after about two days,
- a rash develops,
- you experience flu-like symptoms, or
- you have swollen glands.

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 insects 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 clear up quickly, only lasting for a few hours. But, 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 insects mouth parts are not removed from the skin. However, most tick bites heal within three weeks.

Below are the symptoms that can occur from different types of insect bite:

Midges, mosquitoes, and gnats

Bites from midges, mosquitoes, and gnats often cause small papules (lumps) to form on the 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 occur. Mosquito bites in certain areas of tropical countries can cause malaria. For anti-malarial advice, see the malaria health encyclopaedia topic.

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 and/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, 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 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) and/or papules (lumps). Bites often occur on the face, neck, hands, and arms.

The Blandford fly

The Blandford fly (sometimes called blackfly) is found in an arc running from East Anglia, through Oxfordshire, and into Dorset. Blandford fly bites are common during May and June, and are extremely 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 complications section).

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, as this can make the irritation worse, and can lead to infection.


- Papular urticaria is a condition that is particularly common in children (between the ages of 2-7) and is caused by a hypersensitivity to the bites of fleas, lice, bedbugs, gnats, mites, and other insects. The condition causes lesions and/or papules (small, raised lumps) to develop on or near the area of the bite, or, sometimes, further away. They are usually very itchy and can persist for up to two weeks.


- Bullous reaction is where fluid-filled blisters develop on the 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.

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, or hypotension, 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 1-2 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, such as 40mg/day of prednisolene for 3-5 days (adults).

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. The dosage of prednisolone for adults is 40mg/day, for 3-5 days. For children, it is 1-2 mg/kg once daily for 3-5 days. 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, you can take the necessary steps to get rid of it.

If your pet is the source of the flea infestation, you will need to treat it, its bedding, and household carpets, and soft furnishings with an insecticide. Thoroughly vacuum your carpets and soft furnishings. Limit contact with other pets. 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. Also, do not use petroleum jelly, alcohol, or a lit match to remove a tick, as they won't work.

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

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

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.

In the UK, Lyme disease is uncommon, but the number of cases is rising with 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 occasionally, encephalitis. 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.

For further advice and information about malaria, see the malaria health encyclopaedia topic.

You can take a number of precautions 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.

Precautions that you can take to minimise your risk of being bitten by an insect include:

- if outside, at a time of the day when insects are particularly active, such as at dawn or dusk, cover exposed skin by wearing long sleeves and trousers,


- wear shoes when outdoors,


- apply insect repellent to exposed areas of skin. Repellents that contain DEET (diethyltoluamide) are considered to be the most effective,


- avoid using products with strong perfumes, such as soaps, shampoos, and deodorants, as these attract insects,


- where possible, avoid flowering plants, outdoor areas where food is served, rubbish, and compost areas, and


- remove and destroy insect nests that are in, or near, your house (your local council, or a pest control expert should be able to remove the nest for you).
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.

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.

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. NHSDEC07