Swelling From Bee Stings and Mosquito Bites

Have you ever experienced localized swelling at the site of an insect sting or bite?

Some people are convinced that they have a “severe allergy” to mosquito bites because of the localized swelling that occurs as a result. Others are concerned about a possible “life-threatening reaction” to bee stings because the last time they were stung on the foot, their foot swelled to the point of not being able to put on their shoe.

The truth is, however, that neither of the above examples is considered dangerous.

Bee on person's finger
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Local Reactions to Stings or Bites

Local reactions to insect stings and bites, meaning that the symptoms of swelling, itching, redness, or pain, only occur at or immediately around the site of the bite or sting. These reactions can last up to several days and usually go away on their own without treatment.

Overall, these short-lived local reactions are very common with mosquito bites and bee/wasp/hornet/yellow jacket stings, and may or may not be caused by allergies.

A good tidbit is that people with these types of reactions to mosquitoes may find that taking oral antihistamines a few hours before outdoor activities minimizes these local reactions. In addition, using a good mosquito repellent would likely prevent the bites from occurring in the first place.

If a local reaction does occur, cold compresses can help ease the pain and reduce swelling. Oral antihistamines and oral pain relievers can also help minimize discomfort and itching associated with the reaction.

Finally, you may be surprised to learn that many people notice a reduction in the severity of reactions to mosquito bites over the course of the summer, as the body slowly builds up immunity to the mosquito saliva.

This all being said, a severe allergic reaction, such as anaphylaxis, as a result of a mosquito bite is relatively rare but does occur.

When Local Reaction to Stings or Bites Are Large

A large local reaction to a sting or bite often has the following characteristics:

  • The reaction increases in size for 24 to 48 hours
  • Swelling occurs more than 10cm in diameter at the site of the sting
  • The reaction takes 5 to 10 days to resolve

For a person who has severe or large local reactions as a result of an insect sting, the chance of progressing to anaphylaxis from a future sting is only about 5 to 10 percent. Therefore, no testing or specific treatment is generally required for these reactions.

That being said, if a person is stung frequently and/or stings are unavoidable, venom allergy testing and treatment with venom immunotherapy do work to lessen the severity of future stings (both the size of the local reaction and the duration it occurs).

So in some instances, it may be a good idea for a person with large local reactions to undergo testing and treatment. Of course, this requires a careful discussion between a person and his or her allergist.

In addition, for those people concerned about the small chance of anaphylaxis from a future sting, having an Epi-Pen available in case of anaphylaxis is always prudent. If you do carry an Epi-pen, be sure that you understand when and how to use it.

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By Daniel More, MD
Daniel More, MD, is a board-certified allergist and clinical immunologist. He is an assistant clinical professor at the University of California, San Francisco School of Medicine and currently practices at Central Coast Allergy and Asthma in Salinas, California.