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

• bees (honeybees and bumblebees)
• wasps
• hornets

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.

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 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:

• Africa
• Asia
• South America

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 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

The Blandford fly

The Blandford fly (sometimes called blackfly) is found in:

• East Anglia
• Oxfordshire
• Dorset

Blandford fly bites are common during May and June. They often occur on the legs and are very painful. They can produce a severe, localised reaction (a reaction that is confined to the area of the bite), with symptoms such as:

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

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.

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.

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.

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 (see the Directgov website's section on pest control services for information about how your local council can help).
• 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.