Insect-sting or insect-bite venom can be among the most dangerous allergens. Most people who are stung by bees, yellow jackets, hornets, wasps and fire ants have little to fear. At worst, these individuals may experience mild pain, swelling and itching at the site of the sting.

However, those with allergies to the venom are likely to experience more pronounced effects. A mild allergic reaction may result in nausea, greater swelling and other discomforts. At the other extreme, a rare reaction called anaphylactic shock can impair breathing and heart functions, leading to death in some victims.

Despite the potential danger from insect sting allergies, serious allergic reactions are rare. More that 500,000 people visit emergency rooms each year due to insect stings, according to the American College of Allergy, Asthma and Immunology (ACAAI). However, there are only about 40 deaths each year from insect sting related anaphylaxis. The ACAAI estimates that 0.5 to 5 percent of the population in the United States has severe insect sting allergies.

An individual does not suffer an allergic reaction the first time they are stung by an insect. Instead, the initial encounter leads to sensitization, in which the immune system overreacts to the insect venom and creates immunoglobulin E (IgE) antibodies to fight it. These antibodies trigger an allergic reaction the next time the body encounters the insect venom.

The next time a person is stung, these antibodies cause mast cells to release chemicals such as histamine, which can cause inflammation within the body. Highly allergic individuals may experience anaphylaxis, in which fluid leaks from the bloodstream into the tissues, causing swelling and lowering blood pressure. Bronchial tissues may also swell, causing breathing difficulties.

Adults who experience an anaphylactic episode have a 60 percent chance of having a repeat reaction the next time they are stung, according to the ACAAI, and reactions can be the same or worse. In children, before puberty, the likelihood of a future reaction is much less. People with insect allergies may be advised to get allergy shots to desensitize them to insect stings and bites. They may also be prescribed an allergy kit that contains an epinephrine injection in case of emergencies.