Allergy and Infection from Insect Bites and Stings

Insects bites and stings are unavoidable and every person will experience it several times in life. Most of the time these bites and stings are not serious. It causes some discomfort or pain, may lead to redness and swelling, or even itch for a few hours but eventually resolves without any permanent problems. However, there are instances when complications can arise. The two main complications associated with insect bites and stings are an allergic reaction or an infection.

Insects may only bite or sting as a defense mechanism or as a feeding mechanism.  At most it is intended to allow for the insect to flee or to feed off human tissue and fluids, such as human blood which is consumed by mosquitoes. While most insects that we encounter in everyday life are not venomous, some of these insects may have substances in their saliva that can prevent a blood clot and also irritate the skin.

At other times venom from some of these insects may be delivered at the skin surface with a bite or sting. This can irritate the skin but most are usually not as deadly as the venom from other insects like a scorpion. Instead complications may arise with an abnormally heightened immune reaction (allergy) or with the entry of microbes like bacteria into the deeper skin tissue.

Allergy to Insects Bites/Stings

An allergic reaction is where the immune system overrreacts to a substance due to sensitivity of the immune system. It is important to note that some insect bites and stings may cause a mild allergic reaction in most people due to the substances in the bite or sting, such as the insect’s saliva. This leads to inflammation but it is usually mild and short-lived. However, there are some people who have an exacerbated allergic reaction due to immune hypersensitivity.

These allergic reactions may be localized or generalized. In localized allergic reactions, the inflammation is localized to the site of the bite or sting and the surrounding tissue. Even when severe it is unlikely to be life-threatening. However, a  generalized or systemic allergic reaction can be deadly. This is seen in anaphylaxis where there is inflammation at many sites in the body, well beyond the site of the bite or sting.

In anaphylaxis there reaction can affect sites like the throat and airways. This causes swelling of the tissue which leads to narrowing of the airways. It therefore restricts air flow. There may also be disturbance in heart activity and other parts of the cardiovascular system. Collectively these effects may be life threatening. While the reaction is caused by the insect bite or sting, the effects throughout the body is caused by the immune system.

Infections of Insect Bites/Stings

Another possibility is an infection at the site of an insect bite or sting. A break in the skin as a result of the bite/sting or subsequent scratching that causes skin tears can allow microbs like bacteria to enter the deeper tissue. This may then result in an infection. Most skin infections are localized but if the infection extends deeper, like with cellulitis, then there is a risk that it can rapidly spread to other parts of the body.

The microbes that causes the infections are usually bacteria from the skin surface, in the environment, carried to the site by the fingernails during scratching or from the insect. Staphylococcus aureus and Streptococcus pyogenes are two common bacteria in skin infections. Both of these bacteria are widely distributed throughout the environment across the globe.

Read more on Staph skin infection.

Sometimes bacteria that normally live on the skin surface, like Staphylococcus epidermidis, can also cause an infection when there is a break in the skin. This is more likely to occur in people with a weakened immune system. Unlike allergies, an infection at the site of an insect sting or bite can occur in any person. Scratching the area and not disinfecting the site appropriately are two of the main risk factors that may lead to a skin infection following a bite or sting.

How to Avoid Allergies and Infections

An allergic reaction cannot be prevented in most cases without prompt anti-allergy treatment. People who have known allergies to certain insect bites or stings need to be cautious and carry the necessary medication to counteract these reactions.  This may include antihistamines and epinephrine.

However, skin infections can be avoided with proper wound care and the following preventative measures.

  • Do not scratch the area even though it may be itchy. Topical applications that soothe the itching should be used for itching relief. Since scratching may at times be an unconscious action, ensure that the fingernails are kept short and clean an at all times.
  • Clean the area thoroughly. Run cool water over the site of the bite to ensure that any dust or debris at the site has been removed. If there is a sting or other insect part still impaled at the site then it should be carefully removed and the area washed again.
  • Apply a disinfectant. An antiseptic solution that is suitable for medical use should be applied at the site and surrounding skin to ensure that any microbes, like bacteria, are destroyed. Appropriate disinfecting of the skin at this point is usually sufficient to prevent an infection.
  • Cover the area. Once the area is cleaned and disinfected, it can be covered with an adhesive plaster. This should only be a short term measure to allow the area to heal if there is an open wound. It should not be left on the skin indefinitely and if there is no risk of injuring exposed tissue, it may not be necessary to cover it.
  • Rub an antimicrobial ointment. Apply an antimicrobial ointment at the site of the bite or sting once the disinfectant dries. The ointment should be applied two to three times a day until the wound closes and there are no signs of an infection.

It is important to consult with a medical professional if there is a severe reaction or signs of an infection. Medical treatment may be necessary that may require the use of prescription drugs.


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