For most people, an insect sting is an annoyance that causes some pain or itching. But over 2 million people in the U.S. are allergic to insect stings and over 500,000 Americans end up in the emergency room due to insect stings every year.
Most insect stings in the U.S. are caused by insects known as hymenoptera. These are defined as “membrane-winged” insects and include bees, fire ants, and the group typically called wasps, which includes yellow jackets, paper wasps, and hornets. These insects all inject venom when they sting as part of their natural defenses. When a person is stung, the venom enters the circulatory system and causes the blood vessels to expand. This allows the blood to flow faster which quickly carries the venom into the body.
For most people, an insect sting causes a reaction at the location of the sting which may include pain, itching, and a small amount of swelling. These symptoms usually go away on their own within a few hours or days.
When someone who is allergic to the insect venom is stung for the first time his symptoms may be mild. But his immune system can be sensitized by this first sting to produce an antibody known as immunoglobulin E (IgE) to fight off the allergen. This antibody remains in the body waiting for the next time the allergen is present. A second sting can produce a full allergic reaction which can include swelling in the throat or mouth, dizziness, difficulty breathing, stomach cramps, and nausea or diarrhea. A severe allergic reaction known as anaphylaxis is a full-body reaction that can also cause the blood pressure to drop and can result in death if not treated quickly.
If you have been stung once by an insect and had a large reaction at the site of the sting, such as extreme swelling that was slow to go away, you may be at increased risk of a full allergic reaction if you are stung again. If you believe you are allergic to an insect sting, talk to your doctor to learn how to protect and treat yourself in case you are stung again.
Many people who are allergic to insect stings carry medication called epinephrine or an epi pen that they can quickly inject if they are stung.