| What causes Anaphylaxis | Treatment |
| Symptoms of Anaphylaxis | Conditions that can mimic anaphylaxis |
Anaphylaxis, or anaphylactic shock, is a sudden catastrophic allergic reaction that involves the whole body. It usually occurs within minutes of exposure to the offending allergen (insect stings, nuts and medicines being the commonest causes).
The first documented case of anaphylaxis was in 2641 BC, when King Menes of Egypt died from a Wasp sting.
· Approximately 1 in 500 people attending hospital Emergency Units come because of some form of anaphylactic reaction and the number of new cases in developed countries seem to be rapidly increasing. Possible changes in our diet and environment have been implicated (nut anaphylaxis was first documented only 20 years ago)
Why some
people develop anaphylaxis and others not, is difficult to explain. But it
usually happens to people who are known to have allergies and particularly those
who suffer with
brittle asthma.
The most common cause of anaphylaxis in the community is from eating a food to which you are allergic such as nuts, peanuts, eggs, milk, soya, wheat, fish and shellfish. These 8 foods account for 90% of cases of food induced anaphylaxis. Peanuts and tree nuts (such as Brazil nuts, Hazelnuts, Almonds and Walnuts) are the foods most likely to provoke a reaction.
Even eating a tiny amount
of a particular food can cause anaphylaxis. Some people are so sensitive that
the food essence can trigger a reaction (as in a Restaurant when the person at
the next table is eating fish).
Allergy to venom from wasp stings can cause anaphylaxis as can allergy to latex
and drugs such as penicillin, codeine and aspirin. Bee Allergy is less common in the UK.
In the hospital context, the majority of anaphylactic reactions are to medicines such muscle relaxants, antibiotics and injectable medications including anaesthetic agents. Latex allergy and anaphylaxis is becoming an ever increasing problem, particularly in health workers and children who have frequent operations and are sensitised by exposure to Latex in surgical gloves, drip sets and catheters.
Some people may develop anaphylaxis after eating certain foods such as celery, shrimps, wheat, apple, hazelnut, squid and chicken and exercise after ingesting the food - Exercise Induced Anaphylaxis
Often we never find the cause of the anaphylactic reaction and in 1978 the term "Idiopathic" Anaphylaxis was coined to describe this group of people which accounts for about half of all cases of anaphylaxis.
Anaphylaxis comprises a group of symptoms and features, which in combination lead to a generalised severe allergic reaction with respiratory difficulties and circulatory shock.
The initial reaction is swelling and itching of the area which the allergen has entered. Food for example initially causes swelling and itching of the mouth and throat while a wasp sting will cause intense itching and swelling at the sting site.
A generalised reaction then rapidly follows with an itchy rash that spreads over the whole body. The face and soft tissues begin to swell and breathing becomes difficult. The palms and soles of feet become intensely itchy.
The person becomes very agitated with a “feeling of impending doom”, tightening of the throat and chest occur, while the blood pressure may begin to drop and the victim then loses consciousness.
If you have had a previous and severe anaphylactic reaction, make sure you use the Adrenaline Injector straight away with any future reactions – as any delay puts you at far greater risk for collapse and dying. Although many people carry an Epipen, the most common cause of death is failure to use it. There are two types of injector, one for children and another for adults. The injector is easy to use and is activated by pressing firmly against the front of the thigh muscle. Your doctor should issue you with a “trainer” Epipen to practice self-administration.
If you have always experienced milder attacks with minimal or no breathing difficulties we usually recommend that you immediately take antihistamine medication and monitor the situation for a few minutes before giving adrenaline. Milder symptoms then usually resolve over the next half hour. Always make sure you have someone with you who knows about your condition and who can seek further help if necessary.
Make sure that you do not exert yourself, have a hot bath or get hot, rather remain cool, as increased circulation can lead to more severe and rapid allergic reactions
All people who have had anaphylaxis should go to the local hospital Emergency Unit for further observation. This is because when the adrenaline wears off they may need further treatment, such as antihistamines, corticosteroids and occasionally oxygen and intravenous fluid therapy. We would also recommend that you go to your local hospital and introduce yourself to the medical team so that they are aware of your anaphylactic tendency. There is a risk of developing a delayed reaction 8 to 12 hours after the initial reaction and you should remain in the Emergency Unit for at least 4 hours for observation.
Patients with Idiopathic Anaphylaxis need to stay on oral cortisone for prolonged periods of time to prevent further attacks.
When referred to an
allergy clinic, the specialist will take an extensive “allergy history” to try
and clearly identify the cause of the anaphylaxis. They will then perform
allergy tests on a blood sample using the updated RAST test called a CapRAST.
This test measures specific IgE antibodies in the patient’s blood to the
suspected allergens. Skin Prick Testing is not recommended for diagnosing
anaphylaxis as these tests run the risk of triggering an allergic reaction.
Blood RAST tests are completely safe and the recommended method of testing
for the cause of anaphylaxis. In some situations, patients may have what looks appears to be an
anaphylactic reaction - but which is in fact a fainting spell or sudden drop in
blood pressure. In this situation, we recommend a blood test which measures Tryptase a protein released in the body during anaphylaxis. This is measured in
the blood even hours after the reaction and can usefully confirm that
anaphylaxis has indeed occurred. We can also measure Histamine in the urine a a
marker that anaphylaxis has taken place.
First aid
measures
Emergency care for
someone with suspected anaphylaxis
· If the person is conscious and having breathing difficulties, help them to sit up. If they are shocked with low blood pressure, they are better off lying flat with their legs raised.
· If the person is unconscious, check their airways and breathing and lie them in the recovery position.
· If you know that the person is susceptible to anaphylaxis, check if they carry a preloaded adrenaline syringe (EpiPen). If necessary, help the person to inject it into the muscle of the thigh. This can be administered through clothing.
· Dial 999 for an ambulance and tell the controller that you think the person may have anaphylaxis. If available, antihistamine and steroid tablets should also be given.
How can we prevent anaphylaxis?
If you have ever had an anaphylactic reaction, you must be referred to an
Allergy Clinic for full assessment so as to identify the cause of the reaction.
The following precautions need to be taken to prevent future anaphylactic reactions.
You must have at least two preloaded adrenaline auto-injectors called an Epipen, carry one on your person and keep the other accessible at work or school.
· Never forget to carry your Epipen with you at all times
· Other people at home, work or college must be informed about your allergy, where you keep your Medication and how to use it.
· Make sure that your medication is always easily accessible and that the “expiry date” has not passed.
You must also wear a prominent Medic
Alert bracelet or necklace engraved with information for emergency medical
workers about your specific anaphylactic condition.
Don't put yourself at risk
If you have one anaphylactic reaction there is no predicting how severe the next
reaction might be. Future reactions may be identical, more severe or less
severe. You are however unlikely to ever completely outgrow the allergy and
need to take constant precautions. Never assume that you will be all right just
because you have not had a reaction for some time.
· Check for 'hidden' ingredients on food labels and be very carefully with restaurant food. Foods such as nuts and eggs may have a variety of different names and may be added to processed foods.
· It is wise to seek the advice of an experienced dietician for help with excluding the offending allergen from your diet.
Certain non-allergic conditions can mimic anaphylaxis
Systemic Mastocytosis is a rare condition where a person has a 20-fold increase in Mast Cells in the skin or internal organs - these cells can suddenly release enormous amounts of Histamine and Tryptase after minimal provocation. The result is a reaction that mimics a full blown anaphylactic reaction. The serum Tryptase levels remain highly elevated even between attacks. Systemic Mastocytosis sufferers may have deeply freckled skin (Urticaria Pigmentosa) and associated flushing, headaches, urticaria, asthma, diarrhoea, liver enlargement and osteoporosis with bone pain (a bone biopsy is used in the diagnosis). Their skin typically develops urticarial lesions upon firm stroking - Darier's sign. This condition is commoner in children but thankfully many outgrow the disease by adolescence.
Hereditary Angioedema (HAE) is a familial condition that occurs in 1 in 80 000 people. The typical symptoms begin in adolescence (often females). The painful angioedema (tissue swelling) lasts for 2-3 days and involves the face, neck and limbs with debilitating non-itchy swelling and breathing difficulties. There is a deficiency or under-activity of the C1 Esterase Inhibitor enzyme and very low serum Complement C4 and CH50 on blood testing.
Carcinoid Syndrome can mimic Anaphylaxis but there is usually considerable flushing, diarrhoea, wheezing and an associated right heart murmer with high levels of Hydroxy Indole Acetic Acid in the urine. Phaeochromocytoma is a benign tumour that secretes adrenalin-like chemicals that can mimic anaphylaxis with flushing but is associated with very high blood pressure.
Sometimes Panic Attacks, Hysteria, Aspiration of Foreign substances, Seizures, Histamine-rich foods, Scrombo-toxicity, Lung clots (Pulmonary Embolism), Low blood sugar, Fainting spells and Heart Attacks can closely resemble anaphylactic reactions.
Copyright Dr Adrian Morris 2006
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