Bee and Wasp Sting (cont.)

Most stings arise because an insect perceives a threat to their colony. Bees and wasps commonly sting because an intruder has neared the hive or nest. Loud noises (such as lawn mowers), bright or dark colors, and certain perfumes or perfumed body products may also encourage stings. Some types of insect venom contain pheromones, which attract other members of the colony and induce them to sting.

When bees or wasps sting an individual, they inject venom under the skin of their victim.

• Honey bees, including killer bees, have barbed stingers that tear off when they try to fly away after stinging, so these bees die after the sting and thus can sting only one time. In this case the stinger and venom sac typically remain embedded in the skin of the victim.
  
  
• Bumble bees, hornets, yellow jackets, and wasps are able to sting multiple times, since their stingers are smooth and can be easily withdrawn from the victim's skin.

Bee and wasp venoms vary according to species but typically contain toxic components as well as antigens that stimulate an immune response.

Insect stings may produce four types of reactions, each with characteristic symptoms as below:

1. Local reactions are the most common type of reaction to a bee or wasp sting. Symptoms include pain, swelling, warmth, and redness at the site of the sting. Itching may also be present. These symptoms begin immediately following the sting and often last for only a few hours. Depending upon the type of insect, the stinging apparatus may still be visible in the affected skin. Large local reactions have a greater degree of swelling that can last for up to a week, sometimes associated with nausea and/or tiredness. These reactions are not allergic reactions.
   
   
2. Systemic (body-wide) allergic reactions occur in people who have produced a type of antibody known as IgE antibody against the same insect venom as a result of a previous sting. Systemic allergic reactions are estimated to occur in 0.3% to 3% of stings. Symptoms include hives and flushing of the skin and difficulty breathing due to swelling of the pharynx and epiglottis and narrowing of the bronchial passages. The reaction may vary in severity from mild skin hives to life-threatening reactions. The most severe immunologic reactions are known as anaphylaxis and occur more commonly in males and in people under 20 years of age. In severe reactions, hypotension (low blood pressure), circulatory disturbances, and breathing difficulty can progress to fatal cardiorespiratory arrest. Most people who develop anaphylactic reactions have experienced previous stings with few problems. Once an individual has experienced an anaphylactic reaction, the risk of having a recurrent episode is about 60%.
   
   
3. Toxic reactions are a direct result of toxins in the venom rather than the body's immune response. Most often these are due to multiple simultaneous stings that introduce an unusually large amount of venom into the body. Symptoms can include fever, nausea, vomiting, diarrhea, headache, fainting or dizziness, and convulsions. Hives, rash, and skin symptoms are less common in toxic reactions than in allergic reactions. Because bee and wasp venom are strong stimulants of the immune response, people who have experienced toxic reactions may produce antibodies to the venom and be at risk for future systemic anaphylactic reactions to stings.
   
   
4. Delayed reactions are uncommon and occur even days to weeks after the sting. These reactions constitute less than 0.3% of all reactions to insect stings. The individual's own medical history and condition may play a role in determining whether delayed reactions occur. Symptoms can vary widely and may include inflammation of the brain (encephalitis), the nerves (neuritis), blood vessels (vasculitis), or kidneys (nephritis) as well as blood clotting disturbances. Serum sickness is a type of delayed reaction that occurs a week to 10 days after a sting and may cause itching, rash, fever, joint pain, fatigue, and swollen lymph nodes.

Source: MedicineNet.com
http://www.medicinenet.com/bee_and_wasp_sting/article.htm