A localised allergic skin reaction - occurs in some cases

Some people have an allergic reaction to the venom in a sting. A localised reaction causes swelling at the site of the sting. This becomes larger over several hours, and then gradually goes away over a few days. The size of the swelling can vary, but can become many centimetres across. The swelling may even extend up an entire arm or leg. The swelling is not dangerous unless it affects your airway. However, if it is severe the skin may break out in blisters.

A generalised (systemic) allergic reaction - rare but serious

The venon can cause your immune system to react more strongly. This may cause one or more of the following:

• Itchy skin in many parts of the body, followed by an itchy blotchy rash that can appear anywhere on the body.
• Swelling of your face which may extend to the lips, tongue, throat, and upper airway.
• A sense of impending doom.
• Abdominal cramps and feeling sick.
• Dilation of the blood vessel which can cause:
• general redness of your skin.
• a fast heart rate.
• low blood pressure which can make you feel faint, or even to collapse.
• Wheezing or difficulty in breathing due to an asthma attack or throat swelling.
• A generalised reaction will usually develop within 10 minutes of a sting. It can be fairly mild, for example, a generalised itchy rash and some mild facial swelling. In some cases it is severe and life-threatening, for example, severe difficulty breathing and collapse. A severe generalised allergic reaction is called anaphylaxis and is a medical emergency.

If you have many bee or wasp stings at the same time, this can also cause serious illness. This is usually due to the high dose of venom directly, rather than to an allergy.

Skin infection

Occasionally, a skin infection develops following a bite. Particularly if you scratch a lot, which can damage the skin and allow bacteria (germs) to get in. Infection causes redness and tenderness around the bite. This may spread over several days, and sometimes can become serious.

Transmitted diseases

Most insects in the UK do not transmit other diseases. The main exception is a type of tick which carries a germ called Borrelia burgdorferi which causes Lyme disease. If this germ gets into your skin it can travel to various parts of your body and cause arthritis, meningitis, and other problems. In hot countries, mosquito bites transmit certain germs which can cause diseases such as malaria.

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