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Health Knowledge and Encyclopedia
At your local Pearn's Pharmacy we can offer advice on most general health matters. You can also use our Health Encyclopaedia to provide you with the tools and links you need to pinpoint symptoms and get a full explanation of a suspected condition.
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Insect bites are puncture wounds caused by insects. In the UK, insects that bite include:
When an insect bites, it releases saliva that can cause:
Symptoms of insect bites can vary according to the type of insect involved, and the sensitivity of the person who is bitten. For example, for some people a bite may result in a small, itchy lump that lasts for just a few hours. For others it can lead to 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 the UK, insects that sting include:
See the topic about Insect stings for more information, including how to treat them.
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. Exposing large areas of your skin, such as your arms or legs, leaves you open to being bitten by an insect.
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.
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.
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.
Although some insect bites can cause severe reactions, it is unusual to catch diseases from them in the UK. 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:
Treating insect bites
Most insect bites cause itching and swelling that usually clears up within a few hours. You can treat minor bites by:
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 can be safely treated at home.
Some people are particularly sensitive to certain insect bites and, when they are bitten, react badly to them.
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.
It is important to be aware of 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:
Call 999 for an ambulance if you or someone you know has these symptoms after being bitten or stung by an insect.
Symptoms of an infected bite
Sometimes insect bites can become infected. Symptoms of an infected insect bite may include:
Some bites will naturally be red and swollen, but for other types of bite, these symptoms may not be normal and could indicate an infection.
If you suspect that your bite may have become infected, or you are concerned about your symptoms, see your GP, or call NHS Direct on 0845 46 47.
If you are bitten by an insect, 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:
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.
Types of insect bite
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, you may develop:
Mosquito bites in certain areas of tropical countries can cause malaria (a condition that causes a high temperature and can be fatal). See the topic about Malaria for more information about this condition.
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 a number of itchy red lumps form). Bullae (fluid-filled blisters) may also develop.
Cat and dog fleabites often occur below the knee, commonly around the ankles. They may also affect the forearms if you have 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 experience:
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.
Bites from bedbugs are not usually painful, and if you have not been bitten previously, 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 found in:
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 (a reaction that is confined to the area of the bite), with symptoms including:
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:
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 the 'complications' section).
See the topic about Lyme disease for more information about this condition.
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.^^ Back to top
Insects in the UK that may bite include:
Some risk factors which can make insect bites more likely are listed below.
The diagnosis of insect bites 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 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 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:
Papular urticaria is caused by being very sensitive to insect bites.
Bullous reactions are where fluid-filled blisters develop on your skin. They are particularly common in children, and often occur on the lower legs.
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.^^ Back to top
Most insect bites result in 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, you should visit 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 immediately to request an ambulance.
Small, local reactions
The majority of insect bites cause itching and swelling which usually clears up within several hours. If you were bitten by a tick, you need to remove it (see below).
Small, local reactions can be treated by:
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 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 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.
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.
See the topic about Antihistamines for more information about this type of medicine.
If local swelling is severe, your GP may prescribe a short course of oral corticosteroids to take for three to five days.
See the topic about Corticosteroids for more information about this type of medicine.
If you develop blisters (small pockets of fluid) after being bitten by an insect, do not burst them as 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 topic about Blisters for more information.
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.
If previous insect bites have caused a large skin reaction, such as redness and swelling of over 10cms (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 page about treating allergies for more information about immunotherapy.
If you are bitten by fleas, mites, or bedbugs, you may have an infestation (a large amount of the insects) in your home. You should 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:
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:
For mite infestations, 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. See the Directgov website's section on pest control services for more information about how your local council can help with an infestation.
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 the complications section for more information about this condition.
To remove the tick:
Once 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:
You may need antibiotics to prevent Lyme's disease. See the topic about Lyme disease for more information about this condition, including the symptoms and treatment^^ Back to top
There are a number of complications that can develop after being bitten by an insect.
Secondary bacterial infection
Secondary bacterial infections are a common complication of insect bites. They include:
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 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 Health Protection Agency (HPA) estimates that there are between 1,000 and 2,000 cases of Lyme disease in England and Wales 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:
The condition can also cause damage to the joints which can lead to:
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 West Nile virus in the UK, but 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.
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 1,500 cases of malaria in travellers returning to 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.
See the topic about Malaria for more information about this condition.^^ Back to top
There are a number of precautions 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.
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.
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 should seek medical advice. You may need to take antimalarial tablets to avoid becoming infected. See the 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 to prevent you being bitten.^^ Back to top
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