Author: Unknown
Language: English
Year of publication: 1990
Number of pages: 4
Type of publication: Article
Publisher: unpublished
Publication location: Text on this website

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The sting

Bees only sting as means of defence. Unlike wasps, that can sting repeatedly, the tip of the bee's sting is covered in tiny barbs and these barbs act like fish hooks so that once the sting has penetrated through human skin in cannot be retracted. As the bee pulls herself free the stinging apparatus is torn out of her body and remains behind in the victim's skin. Muscular contractions continue in this stinging apparatus after the bee has torn herself away and the venom continues to be pumped into the wound. The sting must therefore be removed as quickly as possible and the best way to do this is by a scraping action with the fingernail.

 

Bee venom potency is determined by many factors, mainly seasonal, nutritional and the age of the bee. Seasonal and nutritional variation in venom quality is due to the variation of protein the venom. This is determined mainly by the source of pollen that is available (pollen is the main source of a bee's protein intake). The age of the bee influences the quantity and quality of the venom injected as this depends on the development of the stinging apparatus. Young bees have little venom, while bees between 10 and 16 days after hatching produce their maximum quantity of venom. After this age venom production decrease. This does not apply to those bees that live over the dearth period as their venom secretion continues until the colony starts to grow again once the dearth period is finished. These bees really do have a strong sting.

 

Bee venom

Bee venom is composed of a mixture of proteins, peptides and a variety of smaller molecules. The components of venom that cause or enhance toxicity and are responsible for causing an allergic reaction are referred to as antigens. There are many different antigens in bee venom with the five main ones being: phospholipase A, acid phosphatase, hyaluraonidase, melittin and an unidentified allergen Ag-1. These allergens break intracellular barriers allowing venom to spread its toxic effect, causing cellular damage and capable of rupturing blood cells. Any or all of these allergens can cause an antibody-antigen response in hypersensitive individuals causing an allergic reaction.

Melittin as well as being an allergen is also a pain inducer. Other pain inducers in the venom are the smaller molecular compounds such as histamine, acetylcholine and serotonin. These molecules also cause other unpleasant effects such as constriction or dilation of blood vessels, creating swelling.

 

Reaction to bee stings

Reactions to bee stings vary between individuals. The normal reaction is localised around the rae of the sting, but some people build up an allergy to bee antigens, so when they are stung they suffer a whole body reaction that has the potential to be very dangerous.

 

A  normal response

Most people usually only have a slight reaction to their first few stings, but with further stings there is increasing swelling. Excessive swelling can be unsightly, but although unpleasant is not medically dangerous. Stings to the face and heads are serious as the can affect sight or breathing. This increasing local reaction to stings is due to the body building up the antibodies IgE and IgG. It is antibody IgE that is responsible for the allergic reaction and initially people tend to produce IgE faster the IgG. The levels of IgE in response to a sting can therefore cause large local reactions. Eventually, after many stings immunity is achieved as the production of the antibody IgG predominates over that of IgE. The IgG antibody can therefore 'block' the action of the IgE so preventing an allergic type of reaction, and the person can get stung without any reaction to the sting.

 

Treatment

All stings are painful regardless of whether immunity has been achieved or not. When there is a local reaction to the sting treatment can be applied but most treatment offer little more than psychological support. There are some treatments, however, that do seem to help. The best is holding a cold object or putting ice on the injured area to cool and soothe the area. Antihistamine creams that can be purchased for insect bites can also be effective, especially if they contain a local anaesthetic and cooling agent. Some lotions that are used to treat painful sunburn such as calamine lotion can also be effective in relieving itchiness. Where excessive swelling occurs this can often be reduced by applying wet salt or Epsom slats (hydrated magnesium sulphate) as these extract water through the skin by osmosis.

 

Allergic reactions

Hypersensitive reactions to bee stings range in severity but they are all IgE mediated. IgE produced in response to the bee antigens attaches itself to special receptor sites on the basophile and mast cells. The antigens in the venom combine with IgE at the surface of these cells. This antibody-antigen reaction activates and enzyme system in the cells causing degranulation of the cells. This consequently releases substances such as histamine, serotonin, prostaglandins and slow reacting substances of allergic reactions causing an allergic response.

 

Usually 20-30 stings are required before hypersensitivity is detected in an individual. Normally, with this many stings IgG is the main antibody produced in response to bee venom but in hypersensitive individual little of no IgG is produced. IgG acts as a blocking antibody for IgE. Unlike IgE, IgG circulates freely in tissue fluids and bee antigens combine preferentially with the circulating IgG than with the IgE so blocking the interaction of antigens with IgE at the surface of the cell and preventing and allergic reaction.

 

The pattern of development of hypersensitivity in sensitised individuals in highly variable but typically there is some type of increase in sensitivity with increasing numbers of stinging incidents. Hypersensitive reactions can be loosely classified into 3 main types:

• large local responses
• systemic responses
• anaphylaxis

It most be noted however, that there is a great deal of variation in the severity of the response within each of these categories.

 

Large local reactions

In the least severe hypersensitive response to bee stings there is an extensive subcutaneous reaction. Immediately after the sting swelling occurs, then, about 3-4 hours later there is a secondary response where there is further widespread swelling that can take up to 12 hrs or reach its maximum extant. This swelling usually lasts about 2-3 days and is red, sore and itchy.

 

Systemic reactions

Large local reactions often progress to systemic reactions that can be quite serious. Systemic reactions often involve the cardiovascular or respiratory systems giving the symptoms of wheezing, and chest constrictions. Other symptoms such as nausea, vomiting, abdominal pain and light headedness might also be suffered.  The faster such systemic reactions are after a sting gives a rough indication of how serious the reaction is likely to be; reactions occurring within a few minutes are likely to very serious.

 

Anaphylaxis

Anaphylaxis is the most severe type of hypersensitive reaction. It occurs within minutes or even seconds of the sting and can be life threatening. The initial symptoms are similar to the systemic reaction. These are then followed by falling blood pressure causing unconsciousness. Death can occur due to circulatory collapse and respiratory obstruction.

 

Treatment of hypersensitivity

Large local reactions can be treated in much the same way as described for normal reactions. It is also advisable to take an antihistamine tablet after being stung as this helps to reduce the swelling to some extent. The antihistamines that do not caused drowsiness are the best choices.  

 

Systemic reactions are effectively treated with adrenaline. For less severe systemic reactions inhalation of adrenaline should be sufficient. For severe reactions a subcutaneous injection of adrenaline should be given. This should be in the concentration of 0.5-1.0mg as a 1 in 1000 solution for adults and proportionately less for children. Antihistamine tablets can also be taken to reduce the swelling.

 

An anaphylaxis reaction must be treated immediately with an intra-muscular injection of adrenaline of the same concentration as for a systemic reaction. As anaphylaxis is major medical emergency professional medical help must be promptly obtained.

 

Prevention of hypersensitivity

Detection of hypersensitivity in suspected individuals can be measured in one of two ways - the skin test or the RAST test. Both are dependant on the production of the bee venom antibody IgE.

 

The skin test

This is the cheapest and quickest test for hypersensitivity. It is performed by placing a small amount of diluted venom on the forearm after making a scratch so the venom goes into the skin. After 15 minutes the test can be analysed. A positive reaction gives a white raised wheal surrounded by a red flare.

 

The RAST test

This is a radioallergosorbent test that detects the bee venom IgE levels in the blood. As this test requires a blood sample it takes longer to obtain the results and there is greater cost per test. It is however, a safer test to use on highly sensitive individuals as they do not actually come into contact with the venom so there is no risk of anaphylaxis at all.

 

Desensitisation

It is possible to desensitise a hypersensitive individual so they no longer have an allergic reaction to stings but it is an expensive and specialist process. Desensitisation is achieved by subjecting the   hypersensitive individual to injections of increasing concentrations of pure bee venom given at regular intervals. Injections are usually given on a weekly basis and initial doses are extremely low. The actual starting dose depends on the individual but is likely to be as low as 0.01 micrograms. Over time, minutely increasing doses up to 100 micrograms (equivalent to the amount of venom in 2 stings) will be used. 100 micrograms is known as the maintenance dose and once this level has been achieved this does will be injected at monthly intervals until further blood tests confirm immunity has been achieved.

 

There are risks involved with this treatment so it must only be carried out by doctors in places were appropriate medication and equipment are available. Despite the costs, the disadvantages and the length of time required for immunity to be achieved, the success of desensitisation is extremely high. 

 

Put together by an unknown technician at The UK National Bee Unit.