The Australasian Society of Clinical Immunology and Allergy

Most bites and stings result in a localised itch and swelling that settles within a few days. Severe allergic reactions are relatively uncommon. When they do occur, however, bees, wasps and the Australian "Jack Jumper ant" are usually responsible. Fortunately, effective treatments are available to treat allergic reactions.

Reactions to bites are only sometimes serious

• Mosquitoes and "march flies" can cause nasty itchy bites. Serious allergic reactions are very rare, even when the swellings are very large and uncomfortable.
• Caterpillars can cause severe irritation from touching their spines, which are attached to venom sacs underneath the skin.
• Ticks also bite, and occasional life-threatening reactions have been reported.
• Anaphylaxis following snake bites have also been reported, although these are very rare
• Bull ants can occasionally cause anaphylaxis. The major cause of anaphylaxis from ant stings is the Australian "Jack Jumper" ant.

Stinging insects are a common cause of serious allergic reactions

Allergies to venoms from stinging insects are one of the most common causes of serious allergic reactions (anaphylaxis) in Australia. Symptoms include an all-over rash, swelling of tongue or throat, trouble breathing, gut cramps, diarrhoea, vomiting or even a drop in blood pressure (shock). Although these insects are all "hymenoptera" (which means membranous winged insects), their venoms are very different. Allergy to one does not usually increase the risk of reaction to another.

• The Honey Bee is the most common cause of allergic reactions in Australia.
• Paper wasps and European wasps can sting multiple times. The European wasp is becoming an increasing problem in Australia, is particularly aggressive and likes to get inside drink cans at barbeques, although the more familiar "paper wasp" is responsible for the majority of serious stings.
• The Australian "Jack Jumper Ant" (Myrmecia pilosula) is a medium sized black bull-ant prevalent down the eastern side of Australia and Tasmania. It can be recognised by its characteristic "hopping" motion when it walks. It is a very aggressive ant and its stings causes severe local pain. Severe allergic reactions are much more common than is seen with more common bull ants.
• Native Australian bees and the Green Ant of Queensland can also cause allergic reactions.

Natural History of Allergic Reactions

Bites
Local reactions to biting insects like mosquitoes and midges tend to become less severe with time. Unfortunately, reactions to stinging insects (particularly when severe) tend to persist, although children are more likely to improve in children than adults.
Isolated local reactions
Individuals who have had a rash or large local swelling alone have a less than 1 in 10 chance of developing serious allergic reactions with further stings. Immunotherapy is not indicated.
Generalised reactions without life-threatening features
Symptoms of generalised hives without difficulty breathing or a drop in blood pressure are uncomfortable but not dangerous. This type of allergic reactions is more common in children than adults and has less than a 10 % chance of progressing to anaphylaxis. Immunotherapy is not indicated.
Anaphylaxis
Those at greatest risk of further serious reactions are those who have suffered an episode of shock or severe difficulty breathing following a sting. Adults are at greater risk than children. Anyone with a history of a generalised reaction to an insect sting should be referred for a specialist opinion.

Prevention is better than cure

• Bites from midges and mosquitoes are best avoided by covering up as much as possible. Avoid being outdoors in the early morning or at dusk, and use a DEET-containing insect repellent.
• Nightly checks for ticks may help. They should not be removed from allergic subjects until emergency medical facilities are available. This is because allergic reactions often occur when the tick is removed.
• Honey Bees are gentle and normally only sting in self-defense. The best protection is light coloured clothing, covering much of the body (particularly the feet) and avoiding scents.
• Wasps tend to nest in logs, walls or underground. They are generally more aggressive than bees and attracted to food and drink.
• Don't pretend to be a flower! Avoid wearing perfumes and scents. Rapid movement and dark coloured clothing alarm bees. Bright colours and flowery prints attract bees and should also be avoided. White clothing is good, as are muted colours like tan or green.
• Cover up. Stings often occur on bare feet. Allergic people should wear long trousers and shoes when outside and wear gloves when gardening.
• Avoid provoking bees and wasps, have nearby nests removed by professionals, and drive with the windows up and air-conditioner on.
• Schools should have nearby nests removed at the beginning of the school year.
• Be sensible: Drive with car windows up to exclude insects, don't drink "blindly" from drink cans at barbeques and wear shoes.

First Aid is adequate for the treatment of minor reactions

Bees usually leave their barbed sting in the skin and die. Flicking the sting out as soon as possible will reduce the amount of venom injected. Use the edge of your fingernail or credit card, being careful not to squeeze the venom sac, (this will only increase the amount of venom injected). By contrast, wasps and bull ants rarely leave their sting in the skin. Cold packs and soothing creams often help. Sometimes medicines like antihistamines are needed. Patients developing very large uncomfortable local reactions may sometimes need cortisone tablets to settle the swelling.

Serious allergic reactions can be fatal

Deaths from stinging insects result in an average of three deaths per year in Australia. Older individuals and those with severe difficulty breathing are at greatest risk and should be seen by an allergy / immunology specialist for advice.

Diagnosing the cause of your allergy

Your doctor will normally ask a series of questions that may help to narrow down the list of likely cause of your reaction. This approach will also help to exclude conditions that can sometimes be confused with anaphylaxis. Skin or blood (RAST) allergy testing help confirm or exclude potential triggers.

Effective treatment for severe allergic reactions is available

Patients with life-threatening (anaphylactic) reactions are usually advised to:

1. Wear an identifying MedicAlert bracelet, which will increase the likelihood that adrenalin will be administered in an emergency.
2. Avoid medication that may increase the severity of anaphylaxis or complicate its treatment. Beta blockers (and perhaps ACE inhibitors) fall into this group.
3. Seek urgent medical assistance if stung.
4. Carry injectable adrenalin (such as Epipen) to treat severe allergic reactions.

Immunotherapy can reduce the severity of allergy

Immunotherapy (desensitisation) injections can help to "switch off" the allergic reaction over time. This is effective for the treatment of bee and wasp stings. Unfortunately, there is no "vaccine" at this time for treating "jumper ant"allergy, tick allergy or reactions triggered by some other species of ants and wasps.

It is important to realise that immunotherapy is not helpful in patients with large local swellings alone and may not be necessary in patients with isolated rashes. For these reasons, patients should be evaluated by a recognised consultant in clinical immunology and allergy before initiation of immunotherapy is considered. The duration of treatment is generally for at least 3-5 years. 

References

1. Harvey P, Sperber S et al. Med J Aust. 1984, 140: 209-211.
2. Douglas RG, Weiner J.M. et al. J Allergy Clin Immunol 1998; 101: 129-131.
3. Hunt KJ, Valentine MD et al. N Eng J Med 1978; 299: 157-161.
4. Lockey RF, Turkeltaub PC et. al. J Allergy Clin Immunol 1990; 86: 775-780.
5. N Glaspole I, Douglass J. Czarny D. O'Hehir R . Stinging insect allergies. Assessing and Managing. Australian Family Physician 1997; 26 (12):1395-9, 1401.
6. American Academy of Allergy, Asthma an Immunology Committee on Insects. Monograph on Insect Allergy. Third Edition, 1995
7. McGain F, Harrison J, Winkel KD. Wasp sting mortality in Australia. Med J Aut 2000; 173: 198-200.

Content Last updated 17 March 2001