Complications of insect bites and stings 

A number of complications can develop after being bitten or stung by an insect.


Secondary bacterial infections are a common complication of insect bites and stings. They include:

  • impetigo – a highly contagious bacterial infection that causes sores or blisters
  • cellulitis – an infection that makes your skin red, swollen and painful
  • folliculitis – inflammation of one or more hair follicles (the small holes in your skin that hair grows out of)  
  • lymphangitis – an infection that causes red streaks in your armpit or groin and swollen lymph nodes (small glands that are part of the immune system) 

An infection can occur if you scratch an insect bite or sting, or it may be introduced at the time you're bitten.

Infections are usually treated with antibiotics.

Lyme disease

Lyme disease is an infection caused by a species of tick known as Ixodes ricinus. Ticks aren't insects – they're small arachnids.

There are an estimated 2,000-3,000 cases of Lyme disease in England and Wales each year, with about 15 to 20% of cases occurring while people are abroad.

Your risk of developing Lyme disease is increased if you spend a lot of time in woodland or heath areas as these areas are where tick-carrying animals, such as deer and mice, live.

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, such as:

  • meningitis – an infection of the protective membranes that surround the brain and spinal cord
  • facial palsy – weakness of the facial muscles that causes drooping of one or both sides of the face
  • encephalitis – an uncommon but serious condition that causes inflammation of the brain

The condition can also damage the joints, which can lead to arthritis and, occasionally, heart problems, such as inflammation of the heart muscle (myocarditis) and inflammation of the fluid-filled sac that surrounds the heart (pericarditis).

West Nile virus

West Nile virus is an infection with flu-like symptoms that is spread by mosquitoes. 

There have been no reported cases of West Nile virus in the UK, but there have been cases elsewhere in the world. 


Malaria is a tropical disease caused by an infection of the red blood cells. 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 caused by the parasite Plasmodium falciparum is potentially fatal. It accounts for more than half of all cases of malaria in the UK each year.

Page last reviewed: 27/06/2014

Next review due: 27/06/2016