Insect bites and stings

Published by Bupa's Health Information Team, August 2011.

This factsheet is for people who would like information on how to prevent and treat insect bites and stings.

In the UK, being bitten or stung by an insect usually causes no more than a small irritation. However, for some people being bitten or stung can lead to more serious allergic reactions, so it's important to know what to do if this happens.

In countries affected by malaria and other diseases spread by insects, trying not to get bitten is one of the most important aspects of staying healthy.

About bites and stings

In the UK there are a variety of biting and stinging insects, some of which are listed below.

• Common biting insects include flies, fleas, midges, mites and mosquitoes.
• Common stinging insects include bumblebees, honeybees, hornets and wasps.

When an insect bites you, it makes a tiny hole in your skin so that it can reach your blood to feed on it. When you get stung, the insect punctures your skin and injects venom. This venom can cause more serious allergic reactions in some people.

Symptoms of bites and stings

In most people, an insect bite will form a red, itchy spot or lump. These usually clear up within a few days and don’t need any treatment. The same is true of insect stings.

Sometimes a bite or sting can lead to complications such as an allergic reaction or infection. In a few people, bites or stings will cause a more dangerous allergic reaction called anaphylaxis.

Complications of bites and stings

Infection

Insect bites and stings can become infected with bacteria. If this happens, instead of clearing up after a few days, the area around the bite or sting becomes more red and sore, and pus may build up inside. Infected bites or stings may make you feel unwell with flu-like symptoms and swollen glands.

You may also notice a red line coming from the bite and going towards your armpit or groin. This is caused by inflammation in your lymphatic system and is known as tracking. The lymphatic system is the tissues and organs, including the bone marrow, spleen, thymus and lymph nodes, that produce and store cells that fight infection and disease. The channels that carry lymph are also part of this system.

Allergic reaction

If you’re allergic to an insect’s saliva (for a bite) or the venom (for a sting) you may have a more serious reaction. The allergic reaction is usually around the area of the bite or sting, which may become more itchy or swollen. This is called a localised reaction and will probably clear up after a few days.

Your immune system protects you from harmful substances that may enter your body, such as bacteria and viruses. Sometimes your immune system mistakenly recognises something harmless as harmful and reacts to it – this is an allergic reaction. The substance responsible for causing the reaction is called an allergen. For example, if you're allergic to bee stings, the allergen will be the venom from the sting.

To get an allergic reaction, your body needs to have been exposed to an allergen before. This is called sensitisation. 

Anaphylaxis

Some people develop a severe, whole-body allergic reaction to bites or stings called anaphylaxis, or anaphylactic shock. This is a rare but potentially fatal condition.

Symptoms of anaphylaxis can include:

• dizziness
• a rapid pulse
• a sudden drop in blood pressure
• swelling of the airways and throat, making it difficult to breathe
• itching and swelling away from the area where the bite or sting is

Anaphylaxis can lead to the person losing consciousness if he or she doesn’t get immediate medical treatment.

If you have had a serious allergic reaction before, your GP may prescribe a dose of adrenaline to carry with you. Adrenaline is a hormone (a chemical that occurs naturally in your body) that relaxes muscles and so helps to reduce any swelling and make breathing easier. Single doses of adrenaline are available in the form of an EpiPen or AnaPen. This consists of a sterile syringe of adrenaline that is ready to be used in an emergency. Adrenaline should be given within minutes if severe symptoms develop.

As another precaution, it’s wise to wear a medical identification bracelet or tag. This gives details of your allergy and a telephone number that anyone can call for more information in case you develop anaphylaxis.

Treatment for bites and stings

Urgent medical attention is needed for anyone who:

• shows signs of having a severe allergic reaction (anaphylaxis)
  
• has been stung by several insects at the same time
  
• has been stung in the mouth or throat, where the swelling can interfere with breathing

Self-help

Insect bites can be painful or itchy, but try not to scratch them as this can make the symptoms worse. Wash the affected area with soap and water and pat the skin dry.

You can relieve the pain by applying a cold compress (a cloth soaked in iced water).

Stings are typically painful and cause swelling of the skin, but aren't usually dangerous unless you're severely allergic to the venom. If you can see the sting, remove it as soon as possible. You can scrape it out with a fingernail or a credit card. Don't try to grab the sting between your fingers or with tweezers as this can cause the venom sac to squeeze its contents into your skin. 

Medicines

You may wish to use a local anaesthetic spray to reduce pain. A cream or ointment containing hydrocortisone can help reduce swelling and inflammation. You can buy low-dose hydrocortisone cream over the counter but don't use it to treat children under 10, or on your face or on broken or infected skin. Over-the-counter painkillers such as paracetamol can relieve some of the discomfort.

If the lump or itchiness spreads beyond the original site, antihistamine tablets can relieve the symptoms. Some antihistamines may cause drowsiness. This can be an advantage at night when the itchiness might disturb your sleep, but it can be dangerous if you need to drive or operate machinery.

If you have an infected bite or sting, your GP may prescribe an antibiotic lotion or cream to apply to the affected area. For a more severe infection, such as one that is giving you a fever or shows signs of tracking, you may need a course of antibiotics to take by mouth.

Always ask your GP or pharmacist for advice and read the patient information leaflet that comes with your medicine.

Tick bites

Ticks are tiny spider-like creatures (not in fact insects at all) that attach to the skin by their mouth and feed on blood. They usually feed on animals such as sheep and horses. Most often, people are bitten by ticks they have picked up when walking through long grass. If you find a tick attached to your skin, remove it as soon as possible with tweezers by grasping as close as possible to the skin so you don't leave the head or mouth parts behind. Don’t try to dislodge the tick by using petroleum jelly, alcohol or a lit match, as these methods don’t work.

In some areas, particularly where there are wild deer, ticks may carry bacteria called Borrelia burgdorferi that can cause a condition called Lyme disease. If you develop flu-like symptoms or a rash within a few weeks of a tick bite, it's important that you see your GP. Lyme disease can be treated with antibiotics but if left untreated, it can cause more serious symptoms affecting the nervous system, joints and heart.

Prevention of bites and stings

You can reduce your risk of insect bites and stings by:

• wearing insect repellent
• sleeping under a suitable net if mosquitoes are a problem at night
• wearing long sleeves and trousers if you’re outside in the evening, especially near water – tucking trousers into socks or boots, and shirts into trousers will also help
• keeping picnic foods covered up as much as possible – sweet foods and drinks attract insects

Bites and stings abroad

In the UK, the threat to health from insect bites and stings is relatively low. This isn't always the case abroad, and it's important to be aware of the possible risks if you’re travelling to other countries. Your GP can give you up-to-date advice about appropriate preventive treatments.

In tropical countries, malaria is one of the most important issues to consider. In malarial areas, take care not to get bitten by using an insect repellent containing the chemical diethyltoluamide (DEET) and covering up at times when mosquitoes are most active (usually dusk and dawn). Sleeping under a mosquito net is another important way of preventing bites. You should still take these precautions even if you’re taking antimalarial medicines because in tropical countries the insects may carry other diseases too. Also, there is no guarantee that anti-malarial medicines will be 100 percent effective.

For answers to frequently asked questions on this topic, see Common questions.

For sources and links to further information, see Resources.