What are the causes for Allergy: Insect Sting?

An allergic reaction occurs when the immune system of the body overreacts to an "invader" such as insect venom (the allergen). This overreaction is sometimes referred to as a hypersensitivity reaction. The white blood cells produce an antibody to the protein in the venom.
  • The allergic reaction occurs when the antibody, known as immunoglobulin E, or IgE, comes in contact with the protein, either at the first sting or later.
  • IgE promotes release from certain cells of chemicals and hormones called "mediators." Histamine is an example of a mediator.
  • It is the effects of these mediators on organs and other cells that cause the symptoms of the allergic reaction.
Ants, bees, and wasps have a stinger or venom sac and gland on their tail that they use to inject venom.
  • Several stings may occur, particularly if you accidentally disturb a hive or nest.
  • This is particularly true with fire ants and so-called Africanized bees.
  • Africanized bees are the result of breeding of domesticated and wild honeybees in Africa that resulted in a very aggressive honeybee. The venom of these bees is no more potent than that of normal honeybees, but their aggressive nature increases the likelihood that they will swarm and sting you many times, sometimes hundreds of times.
  • Such a large number of stings may result in serious reactions or death, even if you are not allergic to bee venom.
  • If you are allergic to the venom, then you may have an allergic reaction from even a single sting. This is called an anaphylactic reaction. It can be dangerous, even life threatening.
An anaphylactic reaction does not usually occur on the first sting.
  • The immune system makes the antibody at the first sting and stores it on special cells until the next sting. This is called "sensitization."
  • At the first sting, therefore, the body does not have antibodies specific to the venom.
  • Only on a second or later sting can the body mount a major defense against the venom.
  • This is when a life-threatening anaphylactic reaction may occur.
  • Anaphylactic reactions are rare, and do not happen to every person who is stung by an insect.
  • When an anaphylactic reaction seems to occur on the very first sting, probably the person was stung before without realizing it.
Insect venom is used to treat certain medical conditions.
  • In Chinese herbal medicine, the venoms of various insects in this class are used either as direct stings (as a treatment for arthritis and other chronic diseases) or are applied to the skin or the eyes.
  • Such apiotherapy (the medicinal use of honeybee products) may result in an anaphylactic reaction in people who are allergic.
  • Allergy shots given by an allergy specialist also contain venom but are specifically designed to be given to allergic people to reduce their sensitivity to the allergen.

    Source: http://www.emedicinehealth.com