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Travel health: Insect sting allergy - key facts for a Practice Nurse

5 May 2017

Insect sting allergy - key facts for a Practice Nurse

Insect sting allergy – key facts for a Practice Nurse

 

The article was written by the author and supported by a financial grant from ALK-Abello.

What is the prevalence of bee and wasp stings allergy in the UK?

Systemic allergic reactions to insect stings affect up to 5% of the population during their lifetime, and up to 32% of beekeepers1. In the United Kingdom allergic reactions are easily attributed to bees or wasps as there are no other known venomous insects, unlike other countries where hornets, or fire ants, for example, can stimulate allergic responses.

How many deaths in the UK are caused by insect stings?

A study published in 2000 showed that a quarter of anaphylaxis related in the United Kingdom were due to insect venom2. Wasp venom allergy is more common that bee venom allergy3.

Although anybody can develop allergic sensitisation after being stung, bee keepers and their families have the highest incidence for bee sting allergies3. There is no recognised genetic predisposition – repeated stings being the other known risk factor for developing allergy. Individuals with a raised mast cell tryptase are more at risk of developing severe symptoms if they are allergic to venom.

How are allergic reactions classified? What are the symptoms of an allergic reaction to a bee or wasp sting?

Hypersensitivity reactions to bee or wasp venom can be local or systemic, can vary in severity, and are typically of rapid onset. Large local reactions are characterised by oedema, erythema and pruritis, cover more than 10cm in diameter and peak at 24-48 hours after the sting4.

Published guidelines for the treatment of bee and wasp venom allergy by the British Society for Allergy and Clinical Immunology classify systemic reactions as mild, moderate or severe3.        

  • A mild systemic reaction may be characterised by pruritus, urticaria, erythema, mild swelling, rhinitis and conjunctivitis.
  • Moderate systemic reactions may include respiratory wheeze, moderate swelling, abdominal pain, vomiting, diarrhoea and minor or temporary hypotensive symptoms such as feeling feint and dizziness.
  • Severe systemic reactions may include respiratory difficulty such as asthma or laryngeal oedema, hypotension, collapse or loss of consciousness, as well as incontinence and seizures.
     

How quickly do reactions occur?

A “severe” allergic reaction may be characterised as presenting immediately after a sting. The patient may feel unwell with symptoms of hypotension such as dizziness, dimming of vision, a feeling of extreme anxiety or doom, pruritis, urticaria and difficulty in breathing. Mild and moderate symptoms can be difficult to distinguish, clinically, from the effects anyone may experience from a sting. Both can cause local swelling, redness and itching, and the pain of a sting can cause dizziness and difficulty in breathing. Symptoms that occur after 60 minutes or so are unlikely to be due to sensitivity to venom.

How should a suspected wasp and bee sting allergy be investigated?

Correct identification of the type of insect by the patient is not always reliable, so specific IgE to both bee and wasp should be requested.

Patients should be referred to an allergy clinic if:

  • They have received emergency treatment for suspected anaphylaxis5.
     

What are the treatment options?

For mild reactions patients usually carry antihistamines, but as they take some time to reach effective levels they should not be the only treatment carried by patients. Cold compresses can also help to reduce swelling and analgesia, such as paracetamol, may help to reduce the discomfort.

Patients with a history of systemic reactions should be prescribed and shown how to use an adrenaline auto-injector if they have had a systemic reaction to insect venom4. They should also be given a written management plan on self-management of anaphylaxis, i.e. to lie with legs elevated if there is a suggestion of low blood pressure and not to drive or be driven to a hospital but to call an ambulance for help.

As venom allergy is potentially fatal it is recommend that all patients who have, or who are suspected of having, venom allergy should be referred for risk assessment and discussion of treatment options. These are essentially to carry adrenaline and to take reasonable precautions to minimise the risk of being stung4. Immunotherapy (“desensitisation”) may also be a consideration.

 

What happens in an allergy clinic?

A detailed history is taken and a diagnostic test (either Skin prick or Specifiic IgE test) is conducted. An individual risk assessment will be undertaken. Departments offering venom allergy immunotherapy usually have several beekeepers and others who have a relatively high risk of being stung undergoing treatment at any one time. Patients unsuitable for desensitisation have to weigh up the risk of being stung and other risk factors against their specific circumstances with the help of a specialist. Other factors that are considered are those that would influence the outcome of surviving a severe allergic reaction e.g. heart disease, severe asthma and use of beta-blockers.

 

What is Venom Immunotherapy (VIT)?

VIT involves injecting incremental doses of purified bee or wasp venom. It is thought that by doing this over a period of time immunity against the allergen is generated.

A typical course is 3 years3, this may not always be practical due to work commitments or travel to the local specialist centre and these considerations should be discussed at the outset. Immunotherapy is not routinely offered to children with venom allergy as fatalities following a sting are extremely rare.

 

Which patients are eligible for VIT?

Venom immunotherapy is approved by NICE if4:

  • The patient has had a severe reaction to a bee sting, or
  • They have had a moderate reaction to a sting and have a high risk of being stung again, are anxious about future stings or have raised levels of tryptase.

Immunotherapy has its own risk of producing anaphylaxis so patients with brittle asthma, heart problems or who are taking beta-blockers are considered to be of too high a risk. Other factors to take into account include concurrent immunological disease, infection or individuals unwilling to accept the risks/limitations of treatment or unable to comply practically with the treatment regimen.

 

How effective is VIT?

Not all individuals who have undergone immunotherapy will necessarily be stung again, so studies can only estimate the effectiveness but figures of 80-95% are usually quoted3. Unfortunately there is no method of predicting who will remain at risk of anaphylaxis and this should be discussed with any individual undertaking treatment.

 

What can a Nurse in Primary Care do to improve patient care?

  •  Advise patients on ways of how to minimise their risk of further stings3.
  • After emergency treatment for suspected anaphylaxis, offer people a referral to a specialist allergy service5
  • Advise patients to carry two adrenaline auto-injectors at all times6
  • Ensure the devices are in date6
  • The method of administration is brand specific so advise patients to visit the product website to ensure they are confident in using it6 

 

Toolkit:

To download a Venom Allergy referral template please click here:

 

Biography
John Toolan has worked in Clinical Immunology and Allergy nursing in Leeds since 1995. He has been an active member of the Royal College of Nursing (RCN) Allergy and Immunology Nurses Group, having acted as president and treasurer on a number of occasions. John has spoken at conferences and held workshops on a variety of allergy related subjects over the years, and has been involved locally with protocol and guideline composition in relation to Leeds becoming an accredited allergy centre.
During his time in Clinical Immunology and Allergy John has studied for a BA in Humanities and Social Studies, an MA in Social and Cultural History and a post-graduate qualification in Non-Medical Prescribing. These disparate courses have helped him put perspective on the work he does in healthcare and given him a wider viewpoint on the care of allergy service users generally.
 

References

  1. Ludman et al.  Stinging insect allergy – current perspectives on venom immunotherapy. J Asthma Allergy. 2015; 8: 75–86
  2. Pumphrey R. Lessons for management of anaphylaxis from a study of fatal reactions. Clinical and Experimental Allergy 2000; 30:1144-50
  3. Krishna MT, Ewan PW, Diwakar L et al. Diagnosis and management of hymenoptera venom allergy: British Society for Allergy and Clinical Immunology (BSACI) guidelines. Clin Exp Allergy 2011;41:1201–1220
  4. Pharmalgen for the treatment of bee and wasp venom allergy. Feb 2012. NICE TA246.
  5. Anaphylaxis: Assessment and referral after emergency treatment. NICE 2011.December 2011. CG134.
  6. MHRA: AAI’s advice on use. May 2014

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